The uptake of iodide represents the first step in thyroid hormone synthesis by thyroid follicular cells and is mediated by the sodium-iodide symporter (NIS). In mammals, expression of NIS is stimulated by TSH and transcription of the NIS gene involves regulation by the thyroid-specific transcription factors Pax8 and Nkx2.1. In this study, we examined the mRNA expression of NIS, Pax8 and Nkx2.1 in the thyroid gland of Xenopus laevis tadpoles by semi-quantitative reverse transcriptase (RT)-PCR. During spontaneous metamorphosis, NIS mRNA expression was low in premetamorphic tadpoles, increased throughout prometamorphosis, and peaked at climax stage 60. Analysis of TSH beta-subunit (TSHbeta) mRNA in the pituitary of the same tadpoles revealed a close temporal relationship in the expression of the two genes during metamorphosis, suggesting a regulatory role of TSH in the developmental expression of NIS. Treatment of tadpoles with goitrogenic compounds (sodium perchlorate and ethylenethiourea) increased TSHbeta mRNA expression (approximately twofold) and caused thyroid gland hyperplasia, confirming that feedback along the pituitary-thyroid axis was operative. Analysis of gene expression in the thyroid gland revealed that goitrogen treatment was correlated with increased expression of NIS mRNA (approximately 20-fold). In the thyroid gland organ culture experiments, bovine TSH (bTSH; 1 mU/ml) strongly induced NIS mRNA expression. This effect was mimicked by co-culture of thyroid glands with pituitaries from stage 58 tadpoles and by agents that increase intracellular cAMP (forskolin, dibutyryl-cAMP). In addition, it could be shown that thyroid glands of X. laevis tadpoles express Pax8 and Nkx2.1 mRNA in a developmentally regulated manner and that ex vivo treatment of thyroid glands with bTSH, forskolin, and cAMP analogs increased the expression of Pax8 and Nkx2.1 mRNA. This is the first report on developmental profiles and hormonal regulation of thyroid gland gene expression in amphibian tadpoles and, together, results reveal a critical role of TSH in the regulation of NIS mRNA expression in the thyroid gland of X. laevis tadpoles.

Multiple molecular markers contribute to the pathogenesis of thyroid cancer and can provide valuable information to improve disease diagnosis and patient management. We performed a comprehensive evaluation of miRNA gene expression in diverse thyroid lesions (n = 534) and developed predictive models for the classification of thyroid nodules, alone or in combination with genotyping. Expression profiling by reverse transcription-quantitative polymerase chain reaction in surgical specimens (n = 257) identified specific miRNAs differentially expressed in 17 histopathological categories. Eight supervised machine learning algorithms were trained to discriminate benign from malignant lesions and evaluated for accuracy and robustness. The selected models showed invariant area under the receiver operating characteristic curve (AUC) in cross-validation (0.89), optimal AUC (0.94) in an independent set of preoperative thyroid nodule aspirates (n = 235), and classified 92% of benign lesions as low risk/negative and 92% of malignant lesions as high risk/positive. Surgical and preoperative specimens were further tested for the presence of 17 validated oncogenic gene alterations in the BRAF, RAS, RET or PAX8 genes. The miRNA-based classifiers complemented and significantly improved the diagnostic performance of the 17-mutation panel (p < 0.001 for McNemar's tests). In a subset of resected tissues (n = 54) and in an independent set of thyroid nodules with indeterminate cytology (n = 42), the optimized ThyraMIR Thyroid miRNA Classifier increased diagnostic sensitivity by 30-39% and correctly classified 100% of benign nodules negative by the 17-mutation panel. In contrast, testing with broad targeted next-generation sequencing panels decreased diagnostic specificity by detecting additional mutations of unknown clinical significance in 19-39% of benign lesions. Our results demonstrate that, independent of mutational status, miRNA expression profiles are strongly associated with altered molecular pathways underlying thyroid tumorigenesis. Combined testing for miRNA gene expression and well-established somatic gene alterations is a novel diagnostic strategy that can improve the preoperative diagnosis and surgical management of patients with indeterminate thyroid nodules.

The paired box transcription factor Pax8 is critical for development of the eye, thyroid gland as well as the urinary and reproductive organs. In adult, Pax8 overexpression is associated with kidney, ovarian and thyroid tumors and has emerged as a specific marker for these cancers. Recently, Pax8 expression was also reported in human pancreatic islets and in neuroendocrine tumors, identifying Pax8 as a novel member of the Pax family expressed in the pancreas. Herein, we sought to provide a comprehensive analysis of Pax8 expression during pancreogenesis and in adult islets. Immunohistochemical analysis using the most employed Pax8 polyclonal antibody revealed strong nuclear staining in the developing mouse pancreas and in mature human and mouse islets. Astonishingly, Pax8 mRNA in mouse islets was undetectable while human islets exhibited low levels. These discrepancies raised the possibility of antibody cross-reactivity. This premise was confirmed by demonstrating that the polyclonal Pax8 antibody also recognized the islet-enriched Pax6 protein both by Western blotting and immunohistochemistry. Thus, in islets polyclonal Pax8 staining corresponds mainly to Pax6. In order to circumvent this caveat, a novel Pax8 monoclonal antibody was used to re-evaluate whether Pax8 was indeed expressed in islets. Surprisingly, Pax8 was not detected in neither the developing pancreas or in mature islets. Reappraisal of pancreatic neuroendocrine tumors using this Pax8 monoclonal antibody exhibited no immunostaining as compared to the Pax8 polyclonal antibody. In conclusion, Pax8 is not expressed in the pancreas and cast doubts on the value of Pax8 as a pancreatic neuroendocrine tumor marker.

PAX8 and PAX2 are cell-lineage-specific transcription factors that are essential for the development of Wolffian and Müllerian ducts and have recently emerged as specific diagnostic markers for tumors of renal or Müllerian origin. Little is known about their expression in the Wolffian duct-derived human male genital tract. We report our findings of PAX8 and PAX2 expression in the epithelium of the normal male genital tract and in epithelial tumors derived therefrom using immunohistochemistry (IHC). We found that PAX8 and PAX2 were expressed in the epithelium of the male genital tract from the rete testis to the ejaculatory duct. Rare glands in the prostatic central zone, a tissue of purported Wolffian duct origin, were focally positive for PAX2, but no PAX8 was detected in this area, a finding that may warrant further study. We found diffuse expression of PAX8 and PAX2 in 1 case each of serous cystadenoma of the epididymis, carcinoma of the rete testis, Wolffian adnexal tumor of the seminal vesicle, and endometrioid carcinoma of the seminal vesicle. Neither PAX8 nor PAX2 was detected in the seminiferous tubules and interstitium of the normal testis, nor in Leydig cell tumors (n=6), Sertoli cell tumors (n=2), or 48 of 49 germ cell tumors. One pediatric yolk sac tumor showed focal and weak staining for PAX8. Tumors of mesothelial origin, that is, adenomatoid tumors (n=3) and peritoneal malignant mesotheliomas (n=37) in men, were negative for PAX2 and PAX8. Neither PAX2 nor PAX8 was present in other areas of the prostate. Expression of PAX8 and PAX2 in these primary epithelial neoplasms of the male genital tract is due to their histogenetic relationship with Wolffian or Müllerian ducts. PAX8 and PAX2 IHC may facilitate the diagnosis of these tumors and should be included in the differential diagnostic IHC panel.

Dedifferentiated endometrioid adenocarcinoma (DEAC) of the uterus or ovary is characterized by the coexistence of low-grade endometrioid adenocarcinoma and an undifferentiated carcinoma (UC) with solid sheets of medium-sized monotonous epithelial cells. This admixed carcinoma has not been widely recognized, because the solid areas of UC have usually been misdiagnosed as a solid form of FIGO grade 3 endometrioid adenocarcinoma. These tumors have been shown to be clinically aggressive; therefore, accurate diagnosis is necessary for proper patient management. We reviewed our experience with DEACs and compared them with grade 3 endometrioid carcinomas regarding their clinicopathologic, morphologic, and immunohistochemical features. Our results indicate that DEACs are clinically aggressive tumors presented at advanced stages with vascular invasions in 73% and lymph node metastases in 46%. Thirty-eight percent of cases also showed distal metastases. Clinical follow-up data revealed that all patients had either recurrent or metastatic diseases within 3 years of diagnosis, except 1 patient who remained disease free for 3 years after diagnosis. Morphologically, UC components of DEACs were composed of diffuse sheets/solid nests of medium-sized epithelial cells with scant to moderate cytoplasm, uniform vesicular nuclei, and inconspicuous nucleoli. Although UC components of DEACs are variably positive for cytokeratin, EMA, and ER, they are mostly negative for PAX8, except 1 case. Instead, well-differentiated components of DEACs and solid grade 3 endometrioid carcinoma retained all these markers. Our results indicate that DEACs exhibit significantly different clinicopathologic features from grade 3 endometrioid adenocarcinoma, and a combination of immunohistochemical stains can be helpful to differentiate them from each other.

To compare the utility of PAX6 and PAX8 as immunohistochemical markers for neuroendocrine tumors (NETs) of pancreatic origin, we performed PAX6 and PAX8 immunostains on 178 NETs, including 110 primary NETs (26 pancreatic, 10 gastric, 12 duodenal, 22 jejuno-ileal, 10 rectal, 30 pulmonary) and 68 NETs metastatic to the liver (24 pancreatic, 1 duodenal, 37 jejuno-ileal, 1 rectal, 5 pulmonary). Among primary NETs, PAX6 and PAX8 were positive in 65 % (17/26) and 73 % (19/26) of pancreatic, 0 % (0/10) and 10 % (1/10) of gastric, 92 % (11/12) and 92 % (11/12) of duodenal, 0 % (0/22) and 0 % (0/22) of jejuno-ileal, 90 % (9/10) and 80 % (8/10) of rectal, and 0 % (0/30) and 23 % (7/30) of pulmonary NETs, respectively. PAX6 and PAX8 positivity was seen in 46 % (11/24) and 50 % (12/24) of metastatic pancreatic NETs to the liver, respectively. None of the nonpancreatic NETs metastatic to the liver were immunoreactive for either PAX6 or PAX8. PAX6 showed a slightly but statistically significant higher specificity for pancreatic NETs than did PAX8 (P = 0.039), while the sensitivities were similar (P = 0.51). PAX6 had the additional advantages over PAX8 of not exhibiting nonspecific cytoplasmic staining of tumor cells and only infrequently staining background lymphocytes. Since rectal NETs rarely present with metastatic disease, positive staining of a metastatic NET of unknown primary origin for PAX6 and/or PAX8 favors a pancreatic or duodenal origin. This information may be helpful in directing further diagnostic studies to identify the primary site of the metastatic tumor.

Thyroid hormone modulates the expression of numerous genes that in turn regulate lipoprotein metabolism in vivo. We have examined the thyroid hormone-dependent regulation of apolipoprotein B (apoB) RNA editing in a strain of congenitally hypothyroid mice (Pax8(-/-)) that lacks thyroid follicular cells. Neonatal Pax8(-/-) mice demonstrate an approximately 10-fold increase in hepatic triglyceride content associated with a decrease in hepatic apoB RNA editing. Thyroid hormone administration resulted in hepatic triglyceride mobilization in conjunction with an increase in hepatic, but not intestinal, apoB RNA editing and without changing total apoB RNA abundance. ApoB RNA editing is mediated by a multicomponent enzyme complex whose catalytic core contains two proteins, apobec-1 and apobec-1 complementation factor (ACF). Hepatic ACF mRNA and protein abundance decreased in Pax8(-/-) mice, with restoration after thyroid hormone administration, whereas apobec-1 mRNA and protein abundance were unchanged. Immunohistochemical analysis revealed increased staining intensity of ACF within hepatocyte nuclei of treated mice, findings confirmed by Western analysis of isolated nuclei. In vitro RNA editing assays demonstrated that supplementation with recombinant ACF alone restored enzymatic activity of S100 extracts from hypothyroid, Pax8(-/-) mice. These data demonstrate that thyroid hormone modulates murine hepatic lipoprotein metabolism in association with tissue-specific effects on apoB RNA editing mediated through alterations in ACF gene expression.

The stimulation of postprandial K(+) clearance involves aldosterone-independent and -dependent mechanisms. In this context, serum- and glucocorticoid-induced kinase (SGK)1, a ubiquitously expressed kinase, is one of the primary aldosterone-induced proteins in the aldosterone-sensitive distal nephron. Germline inactivation of SGK1 suggests that this kinase is fundamental for K(+) excretion under conditions of K(+) load, but the specific role of renal SGK1 remains elusive. To avoid compensatory mechanisms that may occur during nephrogenesis, we used inducible, nephron-specific Sgk1(Pax8/LC1) mice to assess the role of renal tubular SGK1 in K(+) regulation. Under a standard diet, these animals exhibited normal K(+) handling. When challenged by a high-K(+) diet, they developed severe hyperkalemia accompanied by a defect in K(+) excretion. Molecular analysis revealed reduced neural precursor cell expressed developmentally downregulated protein (NEDD)4-2 phosphorylation and total expression. γ-Epithelial Na(+) channel (ENaC) expression and α/γENaC proteolytic processing were also decreased in mutant mice. Moreover, with no lysine kinase (WNK)1, which displayed in control mice punctuate staining in the distal convoluted tubule and diffuse distribution in the connecting tubule/cortical colleting duct, was diffused in the distal convoluted tubule and less expressed in the connecting tubule/collecting duct of Sgk(Pax8/LC1) mice. Moreover, Ste20-related proline/alanine-rich kinase phosphorylation, and Na(+)-Cl(-) cotransporter phosphorylation/apical localization were reduced in mutant mice. Consistent with the altered WNK1 expression, increased renal outer medullary K(+) channel apical localization was observed. In conclusion, our data suggest that renal tubular SGK1 is important in the regulation of K(+) excretion via the control of NEDD4-2, WNK1, and ENaC.

Thyroid hormone is important for pituitary development and maintenance. We previously reported that in the Pax8(-/-) mouse model of congenital hypothyroidism, lactotrophs are almost undetectable, whereas the thyrotrophs exhibit hyperplasia and hypertrophy. Because the latter might be caused by an overstimulation of thyrotrophs with TRH, we analyzed TRH-R1(-/-)Pax8(-/-) double-knockout mice, which miss a functional thyroid gland and the TRH transducing receptor-1 at pituitary target sites. Interestingly, in these double mutants, the hypertrophy and hyperplasia of the thyrotrophs still persist, suggesting that the phenotype is rather a direct consequence of the athyroidism of the animals. The increased expression of TSH in the Pax8(-/-) mice was paralleled by a strongly up-regulated expression of deiodinase type 2 (Dio2) in thyrotrophic cells. Moreover, coexpression of TSH and Dio2 could also be demonstrated in the pituitary of wild-type mice, underlining the important role of this enzyme in the negative feedback regulation of TSH by thyroid hormone. As another consequence of the athyroidism in the mutant mice, tyrosine hydroxylase mRNA expression was found to be also highly up-regulated in thyrotrophic cells of the pituitaries from Pax8(-/-) mice, whereas the transcript levels in the hypothalamus were not affected. Accordingly, tyrosine hydroxylase protein levels, enzyme activities, and ultimately dopamine concentrations were found to be strongly increased in the pituitaries of Pax8(-/-) mice compared with wild-type animals. These findings may explain in part the reduced number of lactotrophs found in the pituitary of athyroid Pax8(-/-) mice and suggest a novel paracrine regulatory mechanism of lactotroph activity.

Hemangioblastoma is a benign, morphologically distinctive neoplasm of disputed histogenesis that typically occurs in the central nervous system either in the setting of von Hippel-Lindau disease or more often sporadically. Extraneural hemangioblastoma is exceptional and raises a challenging differential diagnosis. Herein, we report a primary renal hemangioblastoma occurring in 51-year-old woman without stigmata of von Hippel-Lindau disease. Histologically, the tumor was composed of sheets of polygonal epithelioid stromal cells with ample pale or eosinophilic, vacuolated cytoplasm in an arborizing capillary network. Tumor cells showed variable nuclear pleomorphism, intranuclear cytoplasmic invaginations, scattered hyaline globules, and psammoma-like calcifications. Some areas showed branching hemangiopericytoma-like vessels with tumor cells radiating from the wall, while other areas were edematous and hyalinized with sparse stromal cells and abundant reticular vessels. Immunohistochemically, the tumor cells reacted strongly and diffusely with antibodies to PAX8, CD10, α-inhibin, S100 protein, neuron-specific enolase, and vimentin, and they showed focal positivity with antibodies to epithelial membrane antigen and AE1/AE3. Tumor cells were negative for CK7, CK8/18, RCC antigen, synaptophysin, chromogranin, c-kit, D2-40, HMB45, melan-A, cathepsin K, SMA, desmin, CD31, CD34, and estrogen and progesterone receptors. Positive immunoreactivity for PAX8 is unexpected and contrasts to central nervous system (CNS) hemangioblastomas, which are essentially always negative for PAX8. This novel finding adds support to the hypothesis that the immunoprofile of extraneural hemangioblastoma varies with site of origin, perhaps as a result of tumor cell lineage and retention of organ-specific markers or acquisition of site-specific antigens due to local factors.

Wilms' tumor (WT) is an embryonal renal neoplasm with features resembling fetal kidney development. A family of genes potentially involved in WT induction is called the paired box (PAX) gene family. In this study we examined by Northern blot analysis the expression of several PAX genes in a variety of WTs and other childhood neoplasms. RNA was isolated from four primary WTs and 12 WTs propagated in nude mice (heterotransplant), as well as from a variety of other childhood renal and nonrenal embryonal tumors. RNA samples were electrophoretically separated in 1.2% agarose gels, transferred to nylon membranes, and hybridized to random primer-labeled PAX2, PAX8, and WT1 probes. Membranes were then exposed to x-ray films at -70 degrees C with intensifying screens. PAX2 and WT-1 expression were seen in all four primary WTs; PAX8 was seen in three of the four primary WTs. Of the 12 heterotransplant Wilms' tumors, PAX2, PAX8, and WT1 were concomitantly expressed in seven tumors. Another heterotransplant WT expressed WT1 alone. Expression of these three genes, with one exception, was not seen in the other childhood renal and nonrenal solid tumors. The PAX genes are transcriptional regulators; their protein products bind to specific DNA segments and control gene expression. Their role in the pathogenesis of Wilms' tumor and their interaction with WT1 are unclear. Elucidation of the functional significance of the PAX genes will provide important insights into not only the pathogenesis of WT but also the molecular control of the developing kidney.

Napsin A is a reliable marker for pulmonary adenocarcinoma and is expressed in a subset of ovarian clear cell carcinomas (O-CCCs), endometrial (EM) CCCs, and endometrioid carcinomas (EC). We investigated napsin A levels in O-CCC and EM-CCC and compared these with levels in other nonmucinous ovarian carcinomas and EM-EC, respectively. Napsin A, thyroid transcription factor (TTF)-1, paired box (PAX) 8, and cancer antigen (CA) 125 expression was evaluated in 111 ovarian and uterine carcinoma cases (22 O-CCC, 15 EM-CCC, 13 ovarian EC (O-EC), 39 high-grade serous carcinoma [HGSC], and 22 EM-EC) using immunohistochemistry. Napsin A immunoreactivity was observed in 21 (95.5%) of 22 O-CCC and 10 (66.7%) of 15 EM-CCC cases but was rare in O-EC and EM-EC (7.7% and 4.5%) and undetectable in HGSC cases. Thyroid transcription factor 1 was not expressed in O-CCC but was detected in 1 (6.7%) of 15 EM-CCC, 3 (23.1%) of 13 O-EC, 2 (5.1%) of 39 HGSC, and 1 (4.5%) of 22 EM-EC cases. All 111 cases examined were positive for PAX8, whereas 3 (20.0%) of 15 of EM-CCC and 1 (4.5%) of 22 EM-EC cases were negative for CA125. There were no napsin A/TTF-1 double-positive cases, except for 1 EM-CCC, in which cells had a focal expression pattern. All napsin A- and/or TTF-1-positive cases expressed PAX8 and CA125. In conclusion, napsin A is frequently expressed in O-CCC and EM-CCC, rarely in O-EC and EM-EC, and never in HGSC cases. These findings confirm the importance of using a panel of antibodies that includes napsin A, TTF-1, and PAX8 when evaluating metastatic carcinomas of unknown origin, particularly when gynecologic and pulmonary adenocarcinomas are included in the differential diagnosis.

Clear cell carcinoma (CCC) of the ovary is an uncommon, but an aggressive epithelial ovarian cancer (EOC), which has overlapping histopathologic features with other ovarian tumours. Lately, Napsin A has been identified as its useful diagnostic immunohistochemical (IHC) marker. Fifty-eight prospectively diagnosed ovarian CCCs, 53 high-grade serous carcinomas (HGSCs), 16 endometrioid adenocarcinomas (EMACs), six mixed carcinomas, containing components of CCC and EMAC, seven metastatic mucinous adenocarcinomas and six ovarian yolk sac tumours (YSTs) were tested for Napsin A immunostaining. Fifty ovarian CCCs, 50 HGSCs, seven ovarian EMACs and five mixed carcinomas were tested for WT1 immunostaining. Napsin A was positively expressed in all 58 (100%) CCCs; was focally positive in 1 of 6 YSTs; in 1/16 EMACs and in six cases of mixed carcinomas, while it was negative in all 53 HGSCs and in seven metastatic mucinous adenocarcinomas. Other IHC markers expressed in cases of CCC ovary were CK7 (31/31) (100%), WT1 (0/50), p53 (20/26, 'wild type'), ER (4/31, focal) (12.9%), PAX8 (14/14) (100%), glypican-3 (4/10, focal) (44.4%), p16INK4 (5/5, focal) and CK20 (0/5). Various IHC markers expressed in HGSCs were WT1 (48/50) (96%), p53 (31/31, mostly 'mutation type'), CK7 (9/9) (100%) ER (13/16, variable) (81.2%) and PAX8 (14/14) (100%). IHC markers expressed in EMACs were ER (15/16) (93.7%), CK7 (2/2) (100%) and WT1 (0/7). IHC markers expressed in mixed carcinomas were CK7 (2/2) (100%), WT1 (0/2), focal Napsin A (6/6) and focal ER (5/6). The sensitivity and specificity of Napsin A for the diagnosis of CCC ovary was 100% and 90.9%, respectively. The sensitivity and specificity of WT1 for diagnosis of HGSC ovary was found to be 96% and 100%, respectively. Napsin A and WT1 are highly sensitive and specific IHC markers for diagnosing ovarian CCCs and HGSCs, respectively, and in differentiating these tumours from their mimics. Napsin A is useful in identification of component of CCC in certain EMACs.

Napsin A and thyroid transcription factor-1 (TTF-1) are useful biomarkers for differentiating lung adenocarcinoma from squamous cell carcinoma and also for differentiating primary lung adenocarcinoma from metastatic lung carcinoma. Pair-boxed 8 (PAX8) can help in distinguishing primary lung carcinoma from metastatic carcinomas and help to determine the primary sites of metastatic carcinomas. Immunohistochemistry for Napsin A, TTF-1, and PAX8 were performed on 193 cases of carcinoma: 50 primary lung carcinoma and 143 carcinomas from other sites. Napsin A and TTF-1 were positive in 54, 52 % of lung carcinomas cases, respectively. While in adenocarcinoma cases, their expressions were 86.7 and 83.3 %, respectively. PAX8 was negative in all lung carcinomas. TTF-1 and PAX8 were positive in 93.3 and 96.7 % of thyroid carcinoma cases and in 87.5 and 93.8 % of papillary carcinoma respectively, and both were positive in 100 % of follicular carcinoma. Napsin A was negative in all thyroid carcinomas. Napsin A and PAX8 were positive in 50 and 93.3 % of renal carcinoma cases and in 81.8 and 100 % of papillary carcinoma, 38.5 and 92.3 % of clear cell carcinoma, and 16.7 and 83.3 % of chromophobe carcinoma respectively. TTF-1 was negative in all renal carcinomas. PAX8 was positive in 80 % of ovarian carcinoma cases; 100 and 60 % of serous mucinous carcinomas, respectively. It was also positive in 100 % of endometrial carcinoma. Napsin A and TTF-1 were negative in both ovarian and endometrial carcinomas. Our data demonstrated that combined use of Napsin A, TTF-1, and PAX8 may help in differentiating between primary lung adenocarcinoma and metastatic lung carcinomas.

BACKGROUND

Well-differentiated thyroid cancer (WDTC) incidence in pediatrics is rising, most being papillary thyroid carcinoma (PTC). The objective of the study was to assess the prevalence of different mutations in pediatric WDTC and correlate the genotype with the clinical phenotype.

METHODS

This is a single-center retrospective study. Thyroid tissue blocks from 42 consecutive pediatric WDTC patients who underwent thyroidectomy between 2001 and 2013 were analyzed at Quest Diagnostics for BRAF(V600E), RAS mutations (N,K,H), and RET/PTC and PAX8/PPARγ rearrangements, using validated molecular methods. Thyroid carcinomas included PTC, follicular thyroid carcinoma (FTC), and follicular variant of PTC (FVPTC).

RESULTS

Thirty-nine samples (29 females) were genotyped. The mean age at diagnosis was 14.7 years (range 7.9-18.4 years), and most were Hispanic (56.4%) or Caucasian (35.9%). The mean follow-up period was 2.9 years. Mutations were noted in 21/39 (53.8%), with both BRAF(V600E) (n = 9), and RET/PTC (n = 6) detected only in PTC. Mutations were detected in 2/5 FTC (PAX8/PPARγ and NRAS) and 3/6 FVPTC cases (PAX8/PPARγ). Of 28 PTC patients, 57.1% had mutations: 32.1% with BRAF(V600E), 21.4% with RET/PTC, and 3.6% with NRAS. Of patients with BRAF(V600E), 77.8% were Hispanic and 88.9% were >15 years, while all RET/PTC-positive patients were ≤15 years (p = 0.003). Tumor size, lymph node involvement, and distant metastasis at diagnosis (or soon after (131)I ablation) did not vary significantly based on the mutation.

CONCLUSIONS

BRAF(V600E) was the most common mutation, especially in older and Hispanic adolescents. A larger, ethnically diverse pediatric cohort followed long term will enable the genotypic variability, clinical presentation, and response to therapy to be better assessed.

Eosinophilic solid and cystic renal cell carcinoma (ESC-RCC) is a novel entity of rare tumors with rather unique morphology and immunohistochemical profile. Until recently these tumors were characterized by indolent behavior. Herein, we describe a series of six primary and metastatic ESC-RCCs morphologically and immunophenotypically mimicking epithelioid angiomyolipoma (eAML). Retrospective review of unclassified RCCs with oncocytic phenotype yielded several candidate cases, 4 of which fulfilled diagnostic criteria after additional work-up. Three female patients and one male (median age 46) presented with unifocal tumors ranging from 1.5 cm to 20.5 cm (median 5 cm). On follow-up (median 32 months), 2 younger patients had no signs of tumor recurrence, but older patients presented with advanced disease. A 50 year-old female developed numerous bone metastases and tumor progression despite aggressive treatment. Two of these metastases were analyzed showing morphology and immunoprofile similar to the primary tumor. 50 year-old male had locally aggressive tumor invading adrenal gland and retroperitoneum. All cases exhibited ESC-like architecture of solid sheets, tight nests and variably sized cysts with hobnailed lining, as well as foci of diffuse growth with poorly cohesive brightly eosinophilic cells. Characteristic cytoplasmic stippling and coarse granularity was present in all cases including compact cytoplasmic "Leishmaniasis-like" globules. Due to high suspicion of eAML, immunostaining panels included melanocytic markers, cytokeratins and RCC-specific markers. All ESC-RCC were positive for CK20 and melanocytic markers Melan-A, Cathepsin-K or HMB45, as well as PAX8, whereas EMA, pan-cytokeratin, CK7, CKIT, CD10, CAIX were negative. Comparison with 5 eAML cases including 2 malignant tumors showed similar morphology and immune reactivity except for more frequent expression of HMB45 and lack of PAX8 positivity. In conclusion, we report 2 cases of aggressive ESC-RCC course including widespread bone metastases in addition to 2 typical indolent tumors. ESC-RCC and eAML could present with overlapping morphology and immunophenotype causing diagnostic difficulty and expanding our understanding of these rare tumors.

BACKGROUND

Thyroid cancers are the most frequently occurring endocrine malignancy worldwide. In Turkey, thyroid cancers are ranked 2(nd) on the incidence list in women, with a rate of 16.2%, but they are not included among the top 10 cancer types in men.

OBJECTIVE

To identify the contribution of the BRAF(V600E) mutation, and the RET/PTC1 and PAX8-PPARγ rearrangements in the diagnosis and differential diagnosis of follicular epithelial-derived thyroid lesions.

METHODS

Retrospective clinical and molecular genetic study.

METHODS

A total of 86 thyroid cases diagnosed between 2001 and 2012 at the Department of Pathology were included in the retrospective study group. Samples best representing the lesion and comprising capsules were chosen in the selection of paraffin blocks pertaining to the cases. The BRAF(V600E) mutation, and the RET/PTC1 and PAX8-PPARγ rearrangements were investigated in all cases.

RESULTS

The BRAF(V600E) mutation was observed in 12 out of 37 papillary carcinoma cases (32.4%), in 1 out of 15 follicular carcinoma cases (6.6%), and in 1 out of 7 undifferentiated carcinoma cases (14.3%). No mutation was detected in benign lesions. The RET/PTC1 rearrangement was detected in 2 out of 7 undifferentiated carcinoma cases (28.6%), and in 1 out of 15 follicular carcinoma cases (6.6%). No gene rearrangement was detected in benign lesions. The PAX8-PPARγ rearrangement was detected in 5 out of 15 follicular thyroid carcinoma cases (33.3%) and in 1 out of 15 follicular adenoma cases (6.6%).

CONCLUSIONS

The BRAF(V600E) mutation and RET/PTC1 rearrangement were effective in distinguishing the follicular epithelium-derived benign and malignant lesions of the thyroid in the resection materials. The BRAF(V600E) mutation was rather specific to papillary carcinoma in the thyroid, and in cases where the BRAF(V600E) mutation was detected, multi-centricity, lymph node metastasis and capsular invasion findings were observed more frequently compared to cases in which no mutation was observed. The PAX8-PPARγ rearrangement was observed to be more effective in the differentiation of adenomas and carcinomas in follicular neoplasms of the thyroid, whereas the RET/PTC1 analysis contributed to the differential diagnosis of papillary carcinoma histogenesis at a frequency of 29% in undifferentiated thyroid carcinomas.

Fine-needle aspiration (FNA) plays a key role in the early evaluation of patients with thyroid nodules; however, from 15% to 30% of FNA specimens are cytologically indeterminate. Molecular testing has proven useful when applied to indeterminate thyroid FNAs, and its use has been endorsed in the American Thyroid Association guidelines. In addition to the noncommercial ("in-house") application of v-Raf murine sarcoma viral oncogene homolog B1 (BRAF), rat sarcoma (RAS), rearranged in transformation/papillary thyroid carcinoma (RET/PTC), and peroxisome proliferator-activated receptor γ/paired box gene 8 (PPARγ/PAX8) testing, there are currently 3 commercially available molecular panels that vary in their relative reported performances, strengths, and limitations. Here, we discuss the role of molecular testing for indeterminate thyroid aspirates, taking into consideration the recent reclassification of the encapsulated follicular variant of papillary thyroid carcinoma (PTC) as "noninvasive follicular neoplasm with papillary-like nuclear features (NIFTP)." Cancer Cytopathol 2017;125(6 suppl):477-85. © 2017 American Cancer Society.

Recurrent gene fusions have been thought to play a central role in leukemias, lymphomas, and sarcomas, but they have been neglected in carcinomas, largely because of technical limitations of cytogenetics. In the past few years, an increasing number of recurrent gene fusions have been recognized in epithelial cancers. The majority of prostate cancers, for example, have an androgen-regulated fusion of one of the ETS transcription factor gene family. Notably, the fusion genes can often serve as specific diagnostic markers, criteria of molecular classification and therefore potential therapeutic targets. Recent studies have focused on investigations of morphologic features (phenotype) of recurrent gene fusions (genotype) in malignancies. In this review, we will summarize the histologic features of known recurrent genomic rearrangements in carcinomas, especially focusing on TMPRSS2-ERG fusion in prostate cancer, EML4-ALK in lung cancer, ETV6-NTRK3 in secretory breast cancer, RET/PTC and PAX8/PPARγ1 rearrangements in thyroid cancer. In addition, we will describe how these features could potentially be used to alert the pathologists of the diagnosis of fusion-positive tumor. A combination of histologic validation with other screening strategies (eg, immunohistochemistry) for recognition of recurrent gene fusions is also highlighted.

Metastatic renal cell carcinoma (RCC) to the urinary bladder is rarely seen. Herein, we report the histologic subtypes, immunohistochemical characteristics, and prognosis of 11 patients with metastatic RCC to the urinary bladder. The mean age at the time of diagnosis of metastatic RCC to the bladder was 66 years (range, 58 to 79 y). There were 9 male and 2 female patients. Four patients presented with hematuria, 2 with urinary retention/obstruction, and 1 with bladder calculi. Four patients were asymptomatic and presented for surveillance cystoscopy, wherein they were found to have bladder masses. Nine patients had prior histories of RCC. The remaining 2 patients presented with metastatic clear cell RCC to the bladder and were subsequently found to have renal masses. The average time between nephrectomy and metastasis to the bladder was 20.7 months (range, 0 to 87 mo). Of the 10 patients with radical/partial nephrectomy, 7 cases were clear cell (2 with sarcomatoid features), 2 papillary, and 1 chromophobe with histologic fidelity between the primary and metastasis. Of cases with available data, the primaries' ISUP nucleolar grades were 2 (n=2), 3 (n=4), and 4 for the 2 cases with sarcomatoid features. In 8 cases, the bladder RCC undermined overlying urothelium with extensive urothelial denudation, and in 3 cases the RCC was free floating without attachment to the urothelium. The 1 chromophobe RCC metastasized with pagetoid spread to a preexisting urothelial papilloma. PAX8 immunohistochemistry was used to confirm the diagnosis in 2 cases. Three patients have no evidence of disease (7, 9, and 13 mo). Two are alive with disease after chemotherapy (30, 37 mo). Six patients are dead of disease with multiorgan metastases; 4 are dead after therapy (5, 8, 25, 28 mo), and two died without radiation or chemotherapy at 10 and 71 months. Metastatic RCC to the urinary bladder is uncommon, with most cases clear cell RCC. In some cases, evidence supports "drop metastases" as the mechanism of spread and patients have relatively long survival. However, in other cases spread to the bladder is in the setting of metastases to other sites, and these patients tended to die relatively shortly after their bladder metastases.

BACKGROUND

The molecular biology and cellular origins of mixed type endometrial carcinomas (MT-ECs) are poorly understood, and a Type II component of 10 percent or less may confer poorer prognoses.

RESULTS

We studied 10 cases of MT-EC (containing endometrioid and serous differentiation), 5 pure low-grade endometrioid adenocarcinoma (EAC) and 5 pure uterine serous carcinoma (USC). Endometrioid and serous components of the MT-ECs were macrodissected and the expression of 60 candidate genes compared between MT-EC, pure USC and pure EAC. We found that four genes were differentially expressed when MT-ECs were compared to pure low-grade EAC: CDKN2A (P = 0.006), H19 (P = 0.010), HOMER2 (P = 0.009) and TNNT1 (P = 0.006). Also while we found that even though MT-ECs closely resembled the molecular profiles of pure USCs, they also exhibit lower expression of PAX8 compared to all pure cases combined (P = 0.035).

CONCLUSIONS

Our data suggest that MT-EC exhibits the closest molecular and epidemiological similarities to pure USC and supports clinical observations that suggest patients with MT-EC should receive the same treatment as patients with pure serous carcinoma. Novel specific markers of MT-EC could be of diagnostic utility and could represent novel therapeutic targets in the future.

Renal cell carcinoma (RCC) associated with neuroblastoma (NB) was included as a distinct entity in the 2004 World Health Organization classification of kidney tumors. A spectrum of RCC subtypes has been reported in NB survivors. We herein describe a series of 8 RCCs diagnosed in 7 patients with a history of NB. Microscopic evaluation, immunohistochemical staining for PAX8, cathepsin K, and succinate dehydrogenase subunit B (SDHB), and fluorescence in situ hybridization (FISH) for TFE3 and TFEB were performed. Four distinct morphologic subtypes were identified: 3 tumors were characterized by cells with abundant oncocytoid cytoplasm and irregular nuclei; 3 showed features of microphthalmia transcription factor family translocation RCC (MiTF-RCC); 1 had features of hybrid oncocytic-chromophobe tumor; 1 had papillary RCC histology. All RCCs expressed PAX8 and retained SDHB expression. Cathepsin K was positive in 2 MiTF-RCCs, 1 was TFEB FISH positive, and the other was indeterminate. Cathepsin K was negative in a third MiTF-RCC with TFE3 rearrangement. TFE3 FISH was negative in 4 and insufficient in 1 of the other 5 RCCs. While a subset of RCCs associated with NB is characterized by cells with prominent oncocytoid cytoplasm, other RCC subtypes also occur in post-NB patients. Renal neoplasms occurring in patients with a history of NB do not represent a single entity but a heterogenous group of RCCs. SDHB mutations do not explain the subset of nontranslocation RCCs with oncocytoid features; therefore, further studies are needed to clarify whether they may represent a distinct entity with unique molecular abnormalities or may belong to other emerging RCC subtypes.

The chromosomal translocation t(2;3)(q13;p25) characterizes a subgroup of tumors originating from the thyroid follicular epithelium and was initially discovered in a few cases of adenomas. Later, a fusion of the genes PAX8 and PPARG resulting from this translocation was frequently observed in follicular carcinomas and considered as a marker of follicular thyroid cancer. According to subsequent studies, however, this rearrangement is not confined to carcinomas but also occurs in adenomas, with considerably varying frequencies. Only five cases of thyroid adenomas with this translocation detected by conventional cytogenetics have been documented. In contrast, studies using reverse-transcription polymerase chain reaction (RT-PCR) detected fusion transcripts resulting from that translocation in an average of 8.2% of adenomas. The aim of this study was to determine the frequency of the PAX8-PPARG fusion in follicular adenomas and to use the HMGA2 mRNA level of such tumors as an indicator of malignancy. In cytogenetic studies of 192 follicular adenomas, the t(2;3)(q13;p25) has been identified in only two cases described herein. Histopathology revealed no evidence of malignancy in either case, and, concordantly, HMGA2 mRNA levels were not elevated. In summary, the fusion is a rare event in follicular adenomas and its prevalence may be overestimated in many RT-PCR-based studies.

BACKGROUND

Congenital hypothyroidism, the most frequent endocrine congenital disease, can occur either based on a thyroid hormone biosynthesis defect or can predominantly be due to thyroid dysgenesis. However, a genetic cause could so far only be identified in less than 10% of patients with a thyroid dysgenesis.

OBJECTIVE

Exome sequencing was used for the first time to find additional genetic defects in thyroid dysgenesis.

METHODS

In a consanguineous family with thyroid dysgenesis, exome sequencing was applied, and findings were further validated by Sanger sequencing in a cohort of 94 patients with thyroid dysgenesis.

RESULTS

By exome sequencing we identified a homozygous missense mutation (p.Leu597Ser) in the SLC26A4 gene of a patient with hypoplastic thyroid tissue, who was otherwise healthy. In the cohort of patients with thyroid dysgenesis, we observed a second case with a homozygous missense mutation (p.Gln413Arg) in the SLC26A4 gene, who was additionally affected by severe hearing problems. Both mutations were previously described as loss-of-function mutations in patients with Pendred syndrome and nonsyndromic enlarged vestibular aqueduct.

CONCLUSIONS

We unexpectedly identified SLC26A4 mutations that were hitherto diagnosed in thyroid dyshormonogenesis patients, now for the first time in patients with structural thyroid defects. This result resembles the historic description of thyroid atrophy in patients with the so-called myxedematous form of cretinism after severe iodine deficiency. Most likely the thyroid defect of the two homozygous SLC26A4 gene mutation carriers represents a kind of secondary thyroid atrophy, rather than a primary defect of thyroid development in the sense of thyroid agenesis. Our study extends the variable clinical spectrum of patients with SLC26A4 mutations and points out the necessity to analyze the SLC26A4 gene in patients with apparent thyroid dysgenesis in addition to the known candidate genes TSHR, PAX8, NKX2.1, NKX2.5, and FOXE1.