The transcription factor for immunoglobulin heavy-chain enhancer 3 (TFE3) is a member of the microphthalmia (MiT/TFE) transcription factor family. Dysregulation of TFE3 due to chromosomal abnormalities is associated with a subset of human renal cell carcinoma. Little structural information of this key transcription factor has been reported. In this study, we determined the crystal structure of the helix-loop-helix leucine zipper (HLH-Lz) domain of human TFE3 to a resolution of 2.6 Å. The HLH-Lz domain is critical for the dimerization and function of TFE3. Our structure showed that the conserved HLH region formed a four-helix bundle structure with a predominantly hydrophobic core, and the leucine zipper region contributed to the function of TFE3 by promoting dimer interaction and providing partner selectivity. Together, our results elucidated the dimerization mechanism of this important transcription factor, providing the structural basis for the development of inhibiting strategies for treating TFE3 dysregulated diseases.

Keywords: Crystal structure; Dimerization; Helix-loop-helix leucine zipper (HLH-Lz) domain; Microphthalmia (MiT/TFE) transcription factor family; Transcription factor E3 (TFE3).

Purpose: Xp11.2 translocation renal cell carcinoma (Xp11.2 tRCC) is a rare subtype of renal cell carcinoma (RCC), characterized by translocations of Xp11.2 breakpoints, involving of the transcription factor three gene (TFE3). The aim of our study was to comprehensively characterize the clinical characteristics and outcomes, and to identify risk factors associated with OS and PFS in Xp11.2 tRCC patients. Methods: Literature search on Xp11.2 tRCC was performed using databases such as pubmed EMBASE and Web of Science. Studies were eligible if outcomes data (OS and/or PFS) were reported for patients with a histopathologically confirmed Xp11.2 tRCC. PFS and OS were evaluated using the univariable and multivariable Cox regression model. Results: There were 80 eligible publications, contributing 415 patients. In multivariable analyses, the T stage at presentation was significantly associated with PFS (HR: 3.87; 95% CI: 1.70 to 8.84; p = 0.001). The median time of PFS was 72 months. In the multivariable analyses, age at diagnosis (HR: 2.16; 95% CI: 1.03 to 4.50; p = 0.041), T stage at presentation (HR: 4.44; 95% CI: 2.16 to 9.09; p < 0.001) and metastasis status at presentation (HR: 2.67; 95% CI: 1.12 to 6.41; p = 0.027) were all associated with OS, with a median follow-up time of 198 months. Conclusion: T stage at presentation is the only factor that is associated with both PFS and OS in patients with Xp11.2 tRCC. Also, patients over 45 or with metastases are more likely to have poorer OS.

Keywords: TFE3; Xp112 translocation renal cell carcinoma; kidney; prognosis; survival.

Clear cell (hemangioblastoma-like) stromal tumor of the lung (CCST-L) is a recently described distinctive rare pulmonary neoplasm of unknown histogenesis and molecular pathogenesis. Only 7 cases have been reported in 2 recent studies, although additional cases might have been reported under the heading of extraneural pulmonary hemangioblastoma. We herein describe 4 CCST-L cases, 3 of them harboring a YAP1-TFE3 fusion. The fusion-positive tumors occurred in 3 women, aged 29, 56, and 69 years. All presented with solitary lung nodules measuring 2.3 to 9.5 cm. Histologically, all tumors showed similar features being composed of relatively uniform medium-sized epithelioid to ovoid cells with clear cytoplasm and small round monomorphic nuclei. Scattered larger cells with enlarged hyperchromatic nuclei and marked pleomorphism were noted in 2 cases. The tumors were associated with a hypervascularized stroma with variable but essentially subtle resemblance to capillary hemangioblastoma and perivascular epithelioid cell tumor (PEComa). Immunohistochemistry was negative for all lineage-specific markers. Targeted RNA sequencing showed a YAP1-TFE3 fusion in 3 of 4 cases. All 3 tumors showed homogeneous nuclear TFE3 immunoreactivity. Two patients were disease free at 36 and 12 months. The third patient had biopsy-proven synchronous renal and hepatic metastases, but extended follow-up is not available (recent case). The fourth case lacking the fusion affected a 66-year-old woman and showed subtle histologic differences from the fusion-positive cases, but had comparable TFE3 immunoreactivity. CCST-L represents a distinctive entity unrelated to hemangioblastoma and likely driven by recurrent YAP1-TFE3 fusions in most cases. The relationship of our cases to the recently reported "hemangioblastoma-like" CCST-L remains to be determined. Analysis of larger series is paramount to delineate the morphologic spectrum and biological behavior of this poorly characterized entity.

Background and aim: Autophagy is a cytoprotective recycling mechanism, capable of digesting dysfunctional cellular components, and this process is associated with pro-survival outcomes. Autophagy may decline in the aging myocardium, thereby contributing to cardiac dysfunction. However, it remains to be established how autophagy responds to ischemia-reperfusion stress with age.

Methods: Samples from the right atrium were collected from young (≤50 years; n = 5) and aged (≥70 years; n = 11) patients before and immediately following cardioplegic arrest during coronary artery bypass grafting surgery, a model of human ischemia-reperfusion injury.

Results: Mitochondrial content, as assessed by a cohort of mitochondrial markers, exhibited an overall decrease in the aging myocardium (p = 0.01). In response to IR, COX-I (0.63 vs. 0.91, p = 0.01) increased in young, but not in aged patients (interaction effect p = 0.08). Reductions in LC3-I (0.48 vs. 0.28, p = 0.02) along with declines in TFEB and TFE3 (0.63 vs. 0.20, p = 0.05; 0.71 vs. 0.20, p = 0.01) were observed with age suggesting an impairment in the aged myocardium. Aged patients also displayed an inability to mount an appropriate response to IR compared to their young counterparts, specifically, increases in v-ATPase and NIX (1.06 vs 0.69, p = .01; 1.15 vs 0.69, p = .001) were not seen in the aged.

Conclusion: Our data demonstrate a reduced cardiac mitochondrial content and a blunted mitochondrial response to ischemia with age, accompanied by a possible impairment in mitophagy. These findings support an age-associated inability of the atrial myocardium to mount appropriate adaptive responses to stress.

Keywords: aging myocardium; autophagy; ischemia-reperfusion; mitochondria; mitophagy.

Xp11 translocation renal cell carcinoma (tRCC) characterized by the rearrangement of the TFE3 is recently identified as a unique subtype of RCC that urgently requires effective prevention and treatment strategies. Therefore, determining suitable therapeutic targets and fully understanding the biological significance of tRCC is essential. The importance of autophagy is increasingly acknowledged because it shows carcinogenic activity or suppressor effect. Autophagy is a physiological cellular process critical to maintaining cell homeostasis, which is involved in the lysosomal degradation of cytoplasmic organelles and macromolecules via the lysosomal pathway, suggesting that targeting autophagy is a potential therapeutic approach for cancer therapies. However, the underlying mechanism of autophagy in tRCC is still ambiguous. In this review, we summarize the autophagy-related signaling pathways associated with tRCC. Moreover, we examine the roles of autophagy and the immune response in tumorigenesis and investigate how these factors interact to facilitate or prevent tumorigenesis. Besides, we review the findings regarding the treatment of tRCC via induction or inhibition of autophagy. Hopefully, this study will shed some light on the functions and implications of autophagy and emphasize its role as a potential molecular target for therapeutic intervention in tRCC.

Keywords: Autophagy; Mechanism; TFE3; Therapy; Xp11 translocation renal cell carcinoma.

BACKGROUND

Because of the rare occurrence of renal cell carcinoma (RCC) among children very little is known about this malignancy in pediatric age. We aimed adding knowledge on the clinical characteristics and outcome of metastatic (m) RCC in children and adolescents.

METHODS

The series included 14 stage 4 RCC patients with a median age at diagnosis of 155.5 months, observed at the Italian Pediatric Hematology and Oncology Association (AIEOP) centers from January 1973 to November 2010. We were able to reevaluate histopatology of 11 out of the 14 patients and perform immunostaining for TFE3 in 9 out of the 11 patients.

RESULTS

Of the 14 patients under study, 5 (3 girls) had a translocation morphology TFE+ RCC, 2 were reassigned as papillary type 1 or 2, respectively, 2 tumor specimens with primary clear cell histology had confirmed the initial histologic diagnosis, and 2-whose biopsy specimen was insufficient-had the diagnosis of RCC not further specified with subtyping. In the remaining 3 cases, the initial diagnosis of clear cell carcinoma was left. Overall, 6 patients received chemotherapy, 9 immunotherapy, and 2 adjuvant antiangiogenic therapy. Overall, 11 patients (78.5%) never achieved complete remission and died from progressive disease 1 to 16 months after diagnosis (median overall survival 5.5 mo). Three patients, 2 of whom received adjuvant antiangiogenic therapy, relapsed to lung at 3, 6, and 8 months after diagnosis, and died 18, 32, and 33 months after diagnosis, respectively.

CONCLUSIONS

Despite their possibly different biology, childhood and adult mRCC seems to be sharing comparable outcomes. Because of the very low incidence of mRCC (about 20%) in children and adolescents, an international pediatric cooperation to address biological studies and assess the novel targeted approaches is needed.

The purpose of classifying neoplasias is to recognize groups with similar progress and prognosis and, if possible, receiving the same treatment. This is why those classifications are systematically being submitted to review and improvement through the new technologies. Differentiation of various entities in renal cancer has been comparatively fast, as the new genetic and molecular discoveries have confirmed the morphologic criteria of the different cell types, thus making it possible to open new therapeutic pathways. Using the current WHO classification we recognize subtypes with excellent prognosis (Multilocular cystic renal carcinoma, Type I renal papillary carcinoma, Tubular and fusocellular mucinous carcinoma), other very aggressive ones (Bellini's collecting duct carcinoma, Medullary carcinoma), and also that the sarcomatoid transformation, even in small areas, impacts the prognosis negatively. Childhood-characteristic renal carcinomas associated with chromosome translocations have been recognized (genetic fusion TFE3 or TFEB), as well as the family forms of renal carcinoma. Regarding the UICC (International Union Against Cancer) classification, there are a series of aspects under argument (size, venous invasion, microvascular invasion, invasion of the adipous tissue of the renal sinus) that shall be discussed too, since it is possible that some modifications of the TNM might occur in the near future.

Perivascular epithelioid cell tumors (PEComas) are rare mesenchymal neoplasms with unpredictable behavior. They are characterized by epithelioid cells, which stain with melanocytic markers, associated with spindle cells reactive for smooth muscle markers. PEComas may be sporadic or associated with the tuberous sclerosis complex, with mutations affecting mostly tuberous sclerosis complex (TSC) 2 and less frequently TSC1 genes. More recently a subtype of PEComa harboring TFE3 gene rearrangement, mutually exclusive with TSC complex mutations, has been identified. The bladder and the other genitourinary tract organs are an infrequent site of origin; to date, only 3 cases of primitive bladder PEComas, 1 prostatic PEComa, and 2 epithelioid angiomyolipomas of the kidney with TFE3 rearrangement have been described in literature. We report a bladder PEComa case with Xp11 rearrangement in a patient who previously had undergone chemotherapy for chronic lymphatic leukemia. We assessed the meaning of the presence of TFE3 rearrangement in genitourinary tract PEComas and the possible correlation of these uncommon lesions with previous chemotherapy. A better understanding of this entity's genetics may help suggest appropriate targeted therapy, which is still lacking in genitourinary tract PEComas.

Keywords: Folpe criteria; Outcome; PEComa of the bladder; Previous chemotherapy; TFE3 translocation.

Xp11.2 translocation renal cell carcinoma (Xp11tRCC) is a subtype of renal cell carcinoma (RCC) characterized by chromosomal rearrangement of the region harboring the transcription factor for immunoglobulin heavy-chain enhancer 3 (TFE3). Xp11tRCCs comprises 20% to 40% of RCCs of children and adolescents and is generally associated with good prognosis. However in adult, the incidence of this tumor is relatively low (1% to 4%), suggesting a more aggressive course. TFE3 gene is fused by translocation to numerous partner genes, and definitive molecular characteristics can be difficult to verify. In this case report, we presented a case of Xp11tRCC with the SFPQ/PSF-TFE3 chimeric gene. The fusion gene was detected by 5'-rapid amplification of cDNA ends (5'RACE). The tumor was found to be in an advanced stage with multiple lymph node metastases. The histological characteristics of the tumor were different from those of XP11tRCC with other more frequently detected fusion genes.

Xp11.2/TFE3 translocation renal cell carcinoma (RCC), a recently classified distinct subtype, is a rare tumor that usually affects children and adolescents. The morphology and biological behavior are not widely recognized, Xp11.2 translocation RCC is suggestive of early metastases despite the small tumor size. The definitive diagnosis requires the evidence of several different reciprocal translocations involving the TFE3 gene located on chromosome Xp11.2. Here, we present a case of Xp11.2 translocation RCC in an 18-yearold male. He was referred to our hospital because of a right renal tumor with macroscopic hematuria and right flank colic. The radiographic evaluation including magnetic resonance imaging (MRI) suggested it to be a typical papillary renal cell carcinoma or benign renal tumor. He underwent laparoscopic nephrectomy against the repeat symptom in spite of small tumor (3.5 cm in diameter). The immunohistochemical study revealed nuclear staining for TFE3 protein in the cancer cells. The urologic and radiologic outcomes were satisfactory after more than 1 year of follow-up.

复合性血管内皮瘤（composite hemangioendothelioma, CHE）是一种少见的中间型血管肿瘤。形态学上，CHE有复杂的结构，由网状、巢状的网状血管内皮瘤样区域和实性片状的上皮样血管内皮瘤样区域组成，部分还出现梭形细胞血管瘤样、Dabska瘤样及高级别血管肉瘤样区域。免疫表达上，瘤细胞表达CD31、ERG、突触素、神经元特异性烯醇化酶，D2-40灶状阳性，而CD34、嗜铬素粒A、CD56、TFE3、CAMTA1阴性。荧光原位杂交检测WWTR1-CAMTA1未见融合信号。随访时间49个月，复发1次，再次手术后辅以放疗，现无症状生存。伴神经内分泌标志物表达的CHE更易发生于深部软组织，形态学上需与其他中间型血管内皮瘤及神经内分泌肿瘤鉴别，生物学行为更具有侵袭性。.

A sclerosing stromal tumor is a very rare benign sex cord-stromal tumor of the ovary. Because its clinical presentation and imaging findings are similar to those of borderline or malignant epithelial tumors and other sex cord-stromal tumors, accurate preoperative clinical diagnosis can be difficult. The aim of this study was to analyze the clinicopathological characteristics of SSTs and examine the immunohistochemical expression TFE3, which has not been studied in SSTs. Our study cohort consisted of 9 patients diagnosed as having SST; the median age was 36 years. Radiologically, SSTs presented as multiseptated cystic masses, mixed echoic masses, pseudolobular masses, solid pelvic masses, or uterine subserosal nodules. In 4 of the 9 cases, the preoperative clinical impression was a borderline or malignant ovarian tumor. SSTs displayed the following histopathological features: 1) relatively well-circumscribed cellular nodules that were randomly distributed in the fibrous or edematous stroma; 2) a characteristic alternating pattern of hypercellular and hypocellular areas; 3) a hemangiopericytoma-like vascular growth pattern in the cellular nodules; 4) bland-looking spindle-shaped cells and round or polygonal cells densely clustered around blood vessels; and 5) red blood cell-containing intracytoplasmic vacuole-like spaces in the tumor cell cytoplasm, possibly indicating epithelioid hemangioendothelioma. Immunohistochemically, the tumor cells exhibited diffuse and moderate-to-strong TFE3 expression in 7 of the 9 SSTs. TFE3 was strongly expressed in the nuclei of round or polygonal cells and lutein cells. In contrast, neither luteinized thecomas nor fibromas appreciably expressed TFE3. In summary, our study describes characteristic histopathological features that may be useful for differentiating SSTs from other sex-cord stromal tumors and demonstrates for the first time that SSTs show strong TFE3 expression. Further investigations are necessary to clarify the role of TFE3 in the development of SSTs.

Alveolar soft part sarcoma is a rare highly malignant neoplasm of the soft tissue and usually occurs in the lower extremities of children and young adults. We report two cases of alveolar soft part sarcoma: a 24-year-old Latino man with a 10-cm neck mass and a 56-year-old Latino woman with a recurring thigh mass. Fine-needle aspiration and a core biopsy were performed on both, which was followed by tumor resection on the man. The smears displayed numerous loosely cohesive or single large cells with abundant granular cytoplasm, round nuclei, vesicular chromatin, and occasional prominent nucleoli. Periodic and Schiff (PAS)-positive, diastase-resistant rhomboid, or needle-shaped crystals were present. Both tumors had diffuse and strong nuclear TFE3 expression and aberrant cytoplasmic CD68 expression. Fluorescence in situ hybridization analysis was performed in the first case, which detected a characteristic translocation t(X;17)(p11;q25). The diagnosis of alveolar soft part sarcoma was rendered in both cases. Herein, we present the cytology, histology, immunohistochemistry, and molecular findings and discuss the differential diagnosis.

Alveolar soft part sarcoma is a very rare, slow growing highly angiogenic tumor with poor prognosis. Most common site in children and infants is head and neck region and in adults it most commonly occurs in extremities especially thigh. In our case study, an 8 years old female patient presented with a gradually progressive left shoulder lump. FNAC from the lesion showed cellular smears with polyhedral and spindly cells showing abundant finely vacuolated cytoplasm, nuclear pleomorphism, intranuclear pseudoinclusions, and few bare nuclei. Perivascular arrangement of cells was peculiar in addition to the presence of intracytoplasmic metachromatic PAS positive diastase resistant granules. A presumptive diagnosis of alveolar soft part sarcoma with differentials of granular cell tumor and PEComa was considered and the lesion was excised. Although the histopathological features were not characteristic (ie, showing mainly solid pattern without classic alveolar pattern), immunohistochemistry were diagnostic (negative for S 100, Desmin, Cytokeratin, EMA, and moderate to strong nuclear positivity for TFE3). Thus, the diagnosis of alveolar soft part sarcoma was established. This case is being presented for its rarity and unique cytological and histopathological features.

Background: Lingual ASPS is extremely rare and aggressive tumor. rearrangement is typically detected in ASPS patients using FISH analysis.

Aim: To present the clinical, histopathological, and radiological features of lingual Alveolar Soft Part Sarcoma.

Method: A 30-year-old male presented with a painless, slowly growing mass of the tongue. Initial impression was of benign vascular lesion. Later, the patient became symptomatic as the mass progressed in size, which necessitated further investigations.

Result: A lip-split, mandibulotomy was performed for the excision of the tumor and revealed an alveolar soft part sarcoma with PAS-positive, diastase resistant intracytoplasmic granules. However, molecular analysis using FISH was negative for TFE3 rearrangement. Patient underwent partial glossectomy with postoperative radiotherapy.

Conclusion: Clinical and pathological correlation of ASPS is very useful to reach a proper diagnosis.

Keywords: glossectomy; lingual cancer; oral; sarcoma; tumor.

Alveolar soft part sarcoma (ASPS) is a very rare soft tissue sarcoma. Primary ASPS of the gastrointestinal tract is especially rare. Due to the scarcity of cases, neither its clinicopathologic features nor its mutational background has been clarified. Here, we report a case of ASPS arising from the rectum, which was completely resected by endoscopic submucosal dissection. The lesion was a 17 × 16 × 15 mm semi-pedunculated mass in the upper portion of the rectum in a 46-year-old female. In terms of histology, tumor cells exhibited confluent eosinophilic cytoplasm, forming a sheet-like architecture. Periodic acid Schiff-positive diastase-resistant intracytoplasmic crystals were observed in the tumor cells. Fluorescence in situ hybridization revealed TFE3 rearrangement, and reverse transcription polymerase chain reaction revealed an ASPSCR1-TFE3 type 1 fusion. Negative PAX8 immunostaining and the absence of other massive lesions in postoperative imaging studies led to a diagnosis of primary ASPS of the rectum. The potential oncogenic role of the canonical ASPSCR1-TFE3 fusion transcript in gastrointestinal ASPS was indicated. Primary gastrointestinal ASPS remains a diagnostic pitfall in routine surgical pathology.

Keywords: ASPSCR1-TFE3 fusion; TFE3; alveolar soft part sarcoma.

Head and neck alveolar soft part sarcoma(ASPS) is a rare, distinctive sarcoma, typically occurring in infants and children.It displays a relatively fast clinical course, and the ultimate prognosis is poor and is often characterised by late metastases. It is now clear that they are caused by the formation of an ASPL TFE3 fusion gene,and the new molecular target therapies under study may change the possible approach to primary disease.The diagnosis and treatment of head and neck ASPS are reviewed in this article.

Myxoinflammatory fibroblastic sarcoma is a soft-tissue neoplasm most frequently found in the distal extremities of middle-aged adults. Most myxoinflammatory fibroblastic sarcoma are low-grade tumors with propensity for local recurrence after incomplete removal. We report a myxoinflammatory fibroblastic sarcoma which developed in the foot of a 41-year-old male and showed an exceptionally aggressive course with metastatic spread and fatal outcome within 16 months. We managed to establish a spontaneously transformed continuous cell line, called JU-PI, from a metastatic lesion. The JU-PI cells have a sub-tetraploid karyotype including the 1;10 chromosomal translocation and amplification of the proximal end of 3p; these features are considered genetic signatures of myxoinflammatory fibroblastic sarcoma. Both the primary tumor and the JU-PI cells showed nuclear expression of the TFE3 transcription factor but TFE3-activating chromosomal rearrangements were not found. To our knowledge, JU-PI is the first established myxoinflammatory fibroblastic sarcoma cell line. JU-PI cells offer a tool for investigating the molecular oncology of myxoinflammatory fibroblastic sarcoma.

Alveolar soft-part sarcoma (ASPS) is a rare distinctive sarcoma, in most cases involving deep soft tissues of the extremities. It is associated with a specific unbalanced translocation, der(17)t(X;17)(p11;q25) that results in the formation of an ASPL-TFE3 fusion gene. Microscopically, it is typified by an alveolar growth of large cells containing typical periodic acid-Schiff-positive rod-shaped crystals, often serving as a diagnostic clue. Other distinctive features include nuclear immunoreactivity for transcription factor 3 (TFE3) protein and a typical ultrastructural finding of large crystals with a rectangular or rhomboid shape. The authors present an unusual case of ASPS with cutaneous involvement, which did not exhibit typical large crystals; there were striking round granules. Molecular genetic study revealed fusion transcript ASPL-TFE3, type 2. To the best of our knowledge, cutaneous involvement of a crystal-deficient ASPS has not been reported.

TFE3 translocation renal cell carcinoma is a highly aggressive malignancy which often occurs primarily in children and young adults. The pathognomonic molecular lesion in this subtype is a translocation event involving the TFE3 transcription factor at chromosome Xp11.2. Hence, the pathological diagnosis of an Xp11.2 translocation RCC is based upon morphology, TFE3 immunohistochemistry, or genetic analyses. However, due to the false-positive immunoreactivity for TFE3 IHC and expensive for TFE3 break-apart FISH assay, additional molecular markers are necessary to help provide early diagnose and individualization treatment. Owing to recent advances in microarray and RNA-Seq, Pflueger et al. have discovered that TMED6-COG8 is dramatically increased in TFE3 translocation RCCs, compared with clear cell RCCs and papillary RCCs, implying that TMED6-COG8 might be a new molecular tumor marker of TFE3 translocation RCCs. To extend this observation, we firstly validated the TMED6-COG8 expression level by qRT-PCR in RCCs including Xp11.2 translocation RCCs (n=5), clear cell RCCs (n=7) and papillary RCCs (n=5). Then, we also examined the expression level of TMED6-COG8 chimera in Xp11.2 translocation alveolar soft part sarcoma. We found that TMED6-COG8 chimera expression level was higher in Xp11.2 translocation RCCs than in ASPS (P<0.05). What's more, the expression levels of TMED6-COG8 chimera in esophagus cancers (n=32), gastric cancers (n=11), colorectal cancers (n=12), hepatocellular carcinomas (n=10) and non-small-cell lung cancers (n=12) were assessed. Unexpectedly, TMED6-COG8 chimera was decreased in these five human types. Therefore, our observations from this study indicated that TMED6-COG8 chimera might act as a novel diagnostic marker in Xp11.2 translocation RCCs.

TFE3 rearrangements are characteristic of alveolar soft part sarcomas (ASPS), Xp11.2 translocation renal cell carcinomas (Xp11-RCC), and other rare tumors. Immunohistochemistry for TFE3 protein has been considered by some to be a reliable surrogate for TFE3 molecular studies, although others disagree. We compared 2 methods for TFE3 immunohistochemistry to determine if technical differences underlie these differences. Ninety-eight archival cases of mixed type, 19 ASPS, and 8 Xp11-RCC were stained for TFE3 at Laboratory A and Laboratory B using routine protocols. Positive controls were normal human testis (Laboratory A) and Xp11-RCC (Laboratory B). Nuclear staining was scored as "negative," "1+" (<10%), "2+" (10%-50%), and "3+" (>50%). Intensity was scored as "negative," "weak," "moderate," or "strong." Only moderate-strong, 2+ or 3+ staining was considered positive. Laboratory A results were as follows: archival cases (42 of 98, 43%), ASPS (16 of 19, 84%), and Xp11-RCC (7 of 8, 88%). Laboratory B results were as follows: archival cases (5 of 98, 5%), ASPS (14 of 19, 74%), and Xp11-RCC (5 of 8, 63%). TFE3 fluorescence in situ hybridization was positive in all tested ASPS and Xp11-RCC. The overall sensitivity and specificity of TFE3 immunohistochemistry for TFE3-rearranged neoplasms were 85% (23/27) and 57% (56/98) at Laboratory A and 70% (19/27) and 95% (93/98) at Laboratory B. Technical differences, in particular, the type of control tissue, likely account for these different results. The results of our study and prior studies suggest that TFE3 immunohistochemistry should play only a minor role (if any) in the diagnosis of TFE3-rearranged tumors, with fluorescence in situ hybridization representing the preferred method.

Our recent study of early-onset unclassified eosinophilic renal cell carcinoma (RCC) demonstrated that two third of cases could be reclassified by performing a limited number of immunohistochemistry stains. Following the same approach, we aimed to investigate what proportion of adult unclassified RCC could be reclassified. We identified 79 cases. The mean age at presentation was 58 years (range, 29 to 84 y). Tumors were grouped based on their predominant morphologic features as oncocytic (n=23); papillary (n=22); clear cell (n=22); mucinous tubular and spindle cell (MTSC; n=5); rhabdoid (n=4); or lacking a dominant pattern (n=3). By reviewing the morphologic features and performing ancillary studies, we were able to reclassify 10 cases (13%). Four cases were positive for CK20 and showed morphologic features consistent with eosinophilic solid and cystic RCC. Four cases were reclassified as MTSC based on VSTM2A expression by RNA in situ hybridization. One case was negative for SDHB and reclassified as succinate dehydrogenase-deficient RCC. None of the cases showed loss of expression of fumarate hydratase. One case was diffusely positive for CK7 and negative for CD117 and reclassified as a low-grade oncocytic tumor. Four cases were positive for both cathepsin-K and TFE3 by immunohistochemistry, although fluorescence in situ hybridization failed to identify rearrangement in either TFE3 or TFEB genes. Of the tumors that remained unclassified, those with oncocytic features were less likely to be a high grade (odds ratio [OR]=0.22, P=0.013) or advanced stage (OR=0.19, P=0.039) and were more common in women (OR=3.4, P=0.05) compared with those without oncocytic features. Tumors with rhabdoid morphology were associated with advanced stage (relative risk=3.6, P=0.009), while tumors with clear cell or papillary features had a wide range of grades and stages at presentation. In summary, the most frequent reclassified entity is eosinophilic solid and cystic RCC. Investigation of expression of succinate dehydrogenase or fumarate hydratase in individuals older than 35 years with unclassifiable tumors is low yield in the absence of specific morphologic features. A subset of MTSC without well-developed morphologic features can be reclassified by using RNA-ISH for VSTM2A. Recognition of more-recently described RCC subtypes allows for their distinction from the unclassified subtype and improves the prognostic information provided.