Alveolar soft part sarcoma (ASPS) is a rare malignancy with high rates of metastasis at presentation, defined by an unclear cellular origin and a unique unbalanced ASPSCR1-TFE3 translocation (der(17)t(X:17)(p11:q25)).¹ ASPS is insensitive to chemotherapy and has been reported to involve the bladder only twice in the pediatric literature; once as a primary malignancy,² and once as a secondary malignancy after cytotoxic chemotherapy.³ Herein, we report the third case of pediatric bladder ASPS in a female patient who received cytotoxic chemotherapy for low-risk neuroblastoma. This would represent the second case of pediatric bladder ASPS as a secondary malignancy after prior chemotherapy.

We report a case of alveolar soft part sarcoma (ASPS) presenting as an isolated frontal lobe metastasis. The tumor demonstrated little or no immunoreactivity for a broad panel of antibodies yet strong, diffuse immunoreactivity with CD68. On electron microscopy, the characteristic rectangular to rhomboid crystalline inclusions of ASPS were not present. Electron-dense granules resembling peroxisomes were present, sometimes in association with elongated granular structures having a periodic, lattice-like arrangement. Metastatic ASPS was confirmed by demonstration of an ASPSCR1-TFE3 fusion and imaging studies that excluded metastatic Xp11.2 translocation renal cell carcinoma. The primary site was subsequently identified in the lower extremity.

BACKGROUND

Alveolar soft part sarcoma (ASPS) is a rare mesenchymal malignancy. ASPS usually occurs most commonly in the deep soft tissues of the thigh and buttock or the head and neck regions. ASPS that originate from the uterine corpus are even more rare, with only 10 previous cases reported in the English literature.

METHODS

In our case, the alveolar features were completely lost and the tumour shows a solid, non-alveolar pattern and the nuclei have marked variation in nuclear size, and multinucleation. The correct pathological diagnosis has been made by immuno- histochemical and ultrastructural features, which rvealed overexpression of TFE3 and peculiar cytoplasmic crystalline inclusions. In this paper, an additional case of primary ASPS of uterine corpus is reported with immunohistochemical, ultrastructural study and review of literature in the effort to delineate its clinical and pathological features. In this unusual site, the diagnosis can be problematic because ASPS can mimic other primary or metastatic uterine neoplasms.

CONCLUSIONS

Thus, in this unusual presentation an essential diagnostic marker is the nuclear over-expression of TFE3 as well as ultrastructural study, which reveals the presence of peculiar cytoplasmic crystalline inclusions.

Alveolar soft part sarcoma (ASPS) is a rare soft tissue sarcoma, but it's easily misdiagnosed in rare locations. The derivation of ASPS is still uncertain, therefore we conducted this study to explore the histogenesis of ASPS by analyzing stem cell markers (ALDH1, CD29, CD133 and Nestin). Protein TFE3 and fusion gene ASPS-TFE3 were tested in paraffin to explore diagnostic strategy and molecular pathological features. In this study, nine cases of ASPS were immunostained with stem cell surface markers (ALDH1, CD29, CD133 and Nestin) and protein TFE3. Seven cases of ASPS mRNA were successfully extracted from nine paraffin-embedded tissues. The expression of fusion gene ASPL-TFE3 was examined by reverse transcriptase-polymerase chain reaction. The immunohistochemical staining of nine patients showed that CD29 and Nestin were negative in all nine cases (0/9). CD133 was weakly positive in one cases (1/9) and ALDH1 was weakly positive in one cases (1/9). TFE3 was positive in nine cases (9/9). Seven paraffin tissues could be successfully extracted with mRNA in nine cases. The results of Reverse Transcription Polymerase Chain Reaction (RT-PCR) showed that ASPL-TFE3 fusion transcripts could be tested in the seven cases (four cases being type 2 and three cases being type 1). The positive rate of CD133 and ALDH1 were less than 1% and the expression of CD29 and Nestin were negative in ASPS. Immunohistochemistry results indicated that the histogenesis of ASPS maybe not derive from mesenchymal stem cells. Immunohistochemistry staining showed that TFE3 protein expression was highly sensitive in ASPS. Furthermore, RT-PCR results showed that fusion gene ASPL-TFE3 (ASPL-TFE3 type 1 and ASPL-TFE3 type 2) was expressed in ASPS, which could provide information for clinical molecular pathological diagnosis and improve the diagnosis rate of rare atypical ASPS.

Alveolar soft-part sarcoma (ASPS) is an extremely rare malignancy characterized by the unbalanced translocation der(17)t(X;17)(p11;q25). This translocation generates a fusion protein, ASPL-TFE3, that drives pathogenesis through aberrant transcriptional activity. Although considerable progress has been made in identifying ASPS therapeutic vulnerabilities (e.g., MET inhibitors), basic research efforts are hampered by the lack of appropriate in vitro reagents with which to study the disease. In this report, previously unmined microarray data for the ASPS cell line, ASPS-1, was analyzed relative to the NCI sarcoma cell line panel. These data were combined with meta-analysis of pre-existing ASPS patient microarray and RNA-seq data to derive a platform-independent ASPS transcriptome. Results demonstrated that ASPS-1, in the context of the NCI sarcoma cell panel, had some similarities to normal mesenchymal cells and connective tissue sarcomas. The cell line was characterized by high relative expression of transcripts such as CRYAB, MT1G, GCSAML, and SV2B. Notably, ASPS-1 lacked mRNA expression of myogenesis-related factors MYF5, MYF6, MYOD1, MYOG, PAX3, and PAX7. Furthermore, ASPS-1 had a predicted mRNA surfaceome resembling an undifferentiated mesenchymal stromal cell through expression of GPNMB, CD9 (TSPAN29), CD26 (DPP4), CD49C (ITGA3), CD54 (ICAM1), CD63 (TSPAN30), CD68 (SCARD1), CD130 (IL6ST), CD146 (MCAM), CD147 (BSG), CD151 (SFA-1), CD166 (ALCAM), CD222 (IGF2R), CD230 (PRP), CD236 (GPC), CD243 (ABCB1), and CD325 (CDHN). Subsequent re-analysis of ASPS patient data generated a consensus expression profile with considerable overlap between studies. In common with ASPS-1, elevated expression was noted for CTSK, DPP4, GPNMB, INHBE, LOXL4, PSG9, SLC20A1, STS, SULT1C2, SV2B, and UPP1. Transcripts over-expressed only in ASPS patient samples included ABCB5, CYP17A1, HIF1A, MDK, P4HB, PRL, and PSAP. These observations are consistent with that expected for a mesenchymal progenitor cell with adipogenic, osteogenic, or chondrogenic potential. In summary, the consensus data generated in this study highlight the unique and highly conserved nature of the ASPS transcriptome. Although the ability of the ASPL-TFE3 fusion to perturb mRNA expression must be acknowledged, the prevailing ASPS transcriptome resembles that of a mesenchymal stromal progenitor.

Keywords: ASPS; Genomics; Mesenchymal; Meta-analysis; Microarray; RNA-seq; Sarcoma; Stromal; Surfaceome; Transcriptome.

Objectives: To present a comprehensive analysis of cytomorphological features, including clinical scenarios of eight, retrospectively diagnosed cases of alveolar soft part sarcoma (ASPS) with TFE3 immunostaining in 7 cases.

Methods: Conventional Papanicolaou (Pap) and May Grunwald Giemsa (MGG) stained smears were critically reviewed in 8 cases, along with their corresponding tissue sections. Various immunohistochemical stains, including TFE3 were tested on tissue sections, using polymer detection technique.

Results: There were 4 males and 4 females, with an age ranging from 17-39 years(average=28.5). The most frequent tumour site was thigh(n=6); followed by shoulder(n=1) and neck(n=1). Tumour size(n=6) varied from 5 cm to 14.5 cm(average=7.2). FNAC was performed for a primary diagnosis in 6 cases and for metastatic lesions in 2 cases. Seven out of 8 cases were correctly diagnosed on cytosmears. On review, the smears were mostly hypercellular(n=5), composed of cohesive clusters(n=8); sharply contoured cell balls with interspersed blood vessels and pseudopapillae(n=3) and singly scattered cells(n=8). The tumour cells were round to oval, containing central to eccentric nuclei(n=8); abundant granular (n=8) to finely vacuolated(n=7); ill- to well-defined cytoplasm; intracytoplasmic rod-like or needle-shaped crystals(n=3) and prominent nucleoli(n=8), In addition, there were binucleated cells(n=7), multinucleate giant cells(n=2), intracytoplasmic inclusions(n=3), intranuclear inclusions(n=2), delicate intercellular fibrillary stroma(n=5) and bare nuclei(n=8). Immunohistochemically, 7/8 tumours were diffusely positive for TFE3.

Conclusions: This constitutes the largest series describing cytomorphological spectrum of ASPS with TFE3 immunostaining results. Certain frequently observed features and rod-like/needle-shaped crystals, on MGG smears, can be useful in differentiating ASPS from its mimics. TFE3 immunostaining is useful in substantiating a diagnosis, in an appropriate clinicoradiological context. A correct diagnosis of ASPS, especially in advanced stage, has treatment implications.

Keywords: FNAC of soft tissue tumours; TFE3; alveolar soft part sarcoma; cytology of alveolar soft part sarcoma.

Both EWSR1 and TFE3 are well-known oncogenes. EWSR1 encodes an RNA-binding protein involved in multiple soft tissue tumors, including Ewing's sarcoma/peripheral neuroectodermal tumor, desmoplastic small round cell tumor, soft tissue clear cell sarcoma (malignant melanoma of soft parts), extraskeletal myxoid chondrosarcoma, and myxoid liposarcomas. TFE3 regulates both Golgi and lysosomal homeostasis and is rearranged in renal cell carcinoma (RCC), alveolar soft part sarcoma, epithelioid hemangioendothelioma, and perivascular epitheloid cell tumors (PEComas). In this report, we found a rare case of RCC with a fusion between 5' EWSR1 and 3' TFE3. The fusion product retained most functional motifs of TFE3. The oncogenic mechanism likely involves TFE3 overexpression through its juxtaposition with the regulatory elements of EWSR1 and its translocation to the nucleus, resulting in the deregulation of Golgi and lysosomal homeostasis. This is a second case of RCC containing EWSR1-TFE3 fusion. This article is protected by copyright. All rights reserved.

The expression of TFE3 (transcription factor E3) in solitary fibrous tumours (SFTs) and their histologic mimickers was investigated, and the diagnostic value and clinical significance of TFE3 nuclear expression in SFTs were explored. Immunohistochemical analysis for TFE3 was performed on 50 cases of SFTs that were surgically resected. The controls were sample tissues from malignant peripheral nerve sheath tumour, synovial sarcoma, dedifferentiated liposarcoma, spindle cell lipoma, and dermatofibrosarcoma protuberans. The survival of patients with TFE3-positive and TFE3-negative expressions was assessed through the Kaplan-Meier analysis. In 44 of 50 (88%) SFTs, nuclear immunoreactivity for TFE3 was detected. The TFE3 expression was negative in all samples of synovial sarcoma, malignant peripheral nerve sheath tumour, dermatofibrosarcoma protuberans, and spindle cell lipoma and weakly positive in 2 of 10 cases of dedifferentiated liposarcoma. Fluorescence in situ hybridization (FISH) confirmed that the expression of the TFE3 protein is not caused by gene translocation. There was no statistical significance between the association of the TFE3 expression and SFT patient prognosis. Therefore, TFE3 is capable of enhancing the differential diagnosis of SFTs and their histologic mimickers and can be potentially used as a diagnostic marker. The findings also offer valuable insights into SFT diagnosis, aetiology, and associated molecular mechanisms.

Transcription factor enhancer 3 (TFE3), on the short arm of chromosome Xp11.23 and its protein, belongs to the microphthalmia transcription family (MiTF) of transcription factors. It shares close homology with another member of the family, MiTF which is involved in melanocyte development. When a cell is stressed and/or starved, TFE3 protein translocates into the nucleus. TFE3 gene fusions with multiple different partner genes occur in several tumours with resultant nuclear expression of TFE3 protein. The main tumours associated with TFE3 gene fusions are: renal cell carcinoma, alveolar soft part sarcoma, a subset of epithelioid haemangioendotheliomas (EHE), some perivascular epithelioid cell tumours and rare examples of ossifying fibromyxoid tumour and malignant chondroid syringoma. TFE3 immunohistochemistry is of use in routine diagnostic practice with the aforementioned tumours harbouring TFE3 fusions leading to nuclear staining. In addition, there are tumours lacking TFE3 fusions but also display TFE3 nuclear immunolabeling, and these include: granular cell tumour, solid pseudopapillary neoplasm of the pancreas and ovarian sclerosing stromal tumour.

Keywords: genes, neoplasm; genetics; oncogenes; sarcoma.

The TFE3 gene is one of four members of the micropathalima-associated transcription factor family, along with TFEB, TFEC, and MiTF, located on chromosome Xp11.2. The site is notable for its involvement in translocation in Xp11 translocation renal cell carcinoma (RCC) and the mesenchymal counterparts, including Xp11 neoplasm with melanocytic differentiation/TFE3 rearrangement-associated perivascular epithelioid cell tumor (PEComa)/ melanotic Xp11 translocation renal cancer/melanotic Xp11 neoplasm, and alveolar soft-part sarcoma. By morphologic, immunohistochemical, genetic, and prognostic similarities, alveolar soft-part sarcoma with the ASPSCR1-TFE3 gene fusion has a closer relationship with Xp11 neoplasm with melanocytic differentiation/TFE3 rearrangement-associated PEComa/melanotic Xp11 translocation renal cancer/melanotic Xp11 neoplasm. These Xp11 translocation mesenchymal neoplasms may represent a distinct entity, which overlaps with Xp11 translocation RCC and broadens the spectrum of Xp11 translocation-associated neoplasms. The impact of individual fusion variants on specific clinicopathologic features of Xp11 translocation RCC has only recently been described. This review provides insight into the clinicopathologic features, prognosis, treatment, and classification of Xp11 translocation RCC and its mesenchymal counterparts, emphasizing the impact of individual fusion variants on specific clinicopathologic features of Xp11 translocation RCC and the relationships among these Xp11 translocation-associated neoplasms.

Transcription factor E3 (TFE3) is a useful marker for tumors with Xp11.2 translocation, including alveolar soft part sarcoma and renal cell carcinoma. Recently, TFE3 overexpression was also found in granular cell tumors (GrCTs). However, the case cohorts of these two studies were limited to only 11 and 6 cases. Whether aberrant TFE3 expression is a common feature of Asian patients with GrCT requires further investigation. In the present study, immunohistochemical staining and TFE3 break-apart fluorescence in situ hybridization (FISH) assay were performed in 45 samples of GrCTs obtained from Chinese patients recruited from three medical centers in northeast China. Diffusive and marked nuclear staining for TFE3 was identified in 11/45 (24%) cases, which was lower than previously reported. Focal or weak TFE3 staining was identified in 13/45 (29%) cases. The remaining 21 cases were negative stained. In addition, GrCTs in subcutaneous tissue exhibited a relatively higher ratio (8/45, 18%) for TFE3 expression, compared with those in other sites. Furthermore, according to FISH data, no rearrangement or amplification of TFE3 was identified in these cases, whether they were positively or negatively stained for TFE3. The results from the present study demonstrated that part of patients GrCTs exhibited TFE3 overexpression, which suggested that this may not be derived from gene rearrangement.

We have constructed two YAC contigs in the Xp11.23-p11.22 interval of the human X chromosome, a region that was previously poorly characterized. One contig, of at least 1.4 Mb, links the pseudogene OATL1 to the genes GATA1, TFE3, and SYP and also contains loci implicated in Wiskott-Aldrich syndrome and synovial sarcoma. A second contig, mapping proximal to the first, is estimated to be over 2.1 Mb and links the hypervariable locus DXS255 to DXS146, and also contains a chloride channel gene that is responsible for hereditary nephrolithiasis. We have used plasmid rescue, inverse PCR, and Alu-PCR to generate 20 novel markers from this region, 1 of which is polymorphic, and have positioned these relative to one another on the basis of YAC analysis. The order of previously known markers within our contigs, Xpter-OATL1-GATA-TFE3-SYP-DXS255146- Xcen, agrees with genomic pulsed-field maps of the region. In addition, we have constructed a rare-cutter restriction map for a 710-kb region of the DXS255-DXS146 contig and have identified three CPG islands. These contigs and new markers will provide a useful resource for more detailed analysis of Xp11.23-p11.22, a region implicated in several genetic diseases.

This is a case report of a 46-year-old white male who presented with dyspnea. Thoracic and abdominal examinations showed a heterogeneously enhancing mass in the right kidney, multiple pulmonary nodules, and left pleural thickening with large pleural effusion. Pleura biopsy revealed a malignant neoplasm composed of cells with predominantly clear cytoplasm. Considering the large mass in the right kidney, clear cell renal cell carcinoma (RCC) was the main differential diagnosis. The diagnosis in this case was not definitive by histology alone since clear cell RCC markers such as RCC and AE1/AE3 were negative, and CD10 was only focally positive. Transcription factor E3 (TFE3) immunohistochemistry was positive, while the XP11.2 translocation testing was negative. Electron microscopy demonstrated that the tumor cells had abundant cytoplasmic glycogen and lipid, focal long microvilli lining rare lumina, and adjacent interdigitating cell membranes joining the neoplastic cells, indicating a diagnosis of renal clear cell carcinoma. In addition, numerous crystalline-like dense granules were identified in the cytoplasm of the neoplastic cells, which are reminiscent of those typically seen in alveolar soft part sarcoma and rarely described in XP11.2 translocation RCC. Overall, this renal tumor likely represents a variant of XP11.2 translocation RCC, overexpressing TFE3 with dense granules.

Objective: To study the clinicopathological features, diagnosis, and differential diagnosis of atypical epithelioid hemangioendothelioma (EHE). Methods: Eight cases of atypical EHEs were collected from Jiangsu Province Hospital (the First Affiliated Hospital of Nanjing Medical University) between 2010 and 2018. EnVision method and fluorescence in situ hybridization (FISH) were used to detect immunophenotype, WWTR1-CAMTA1 and TFE3 gene rearrangement, respectively. Results: There were 4 males and 4 females, ranging from 42 to 59 years (median 47.5 years). The tumors located in soft tissue (3 cases), lung (3 cases), liver (1 case) and chest wall (1 case). One soft tissue EHE involved also adjacent fibula and pleural involvement was present in all three lung cases at the diagnosis. Regional lymph node metastases were present in two cases (one involving soft tissue tumor and one involving liver). Morphologically, the tumor cells were epithelioid with abundant eosinophilic cytoplasm, moderate to marked nuclear pleomorphism, irregular nuclear membrane, unevenly chromatin, and prominent nucleoli. The cells arranged in cords, small nests or solid pattern. The mitotic rate was 4.3 mitoses/2 mm(2) on average (ranging 2 to 9). Tumor necrosis was seen in every case. Among all 8 cases, blister cells were found upon careful observation. Myxohyaline stroma was present in 6 cases. Immunohistochemically, tumor cells expressed CD31 (8/8), CD34 (7/8), ERG (8/8), CKpan (2/7), and CAMTA1 (4/6). None of the tested cases stained for TFE3 (0/6). WWTR1-CAMTA1 fusion gene by FISH was found in all tested 6 cases and TFE3 gene rearrangement was not detected in any. Available clinical follow-up was obtained in 7 cases and the intervals range from 6 to 55 months (average 19.6 months). Six patients had metastasis and 3 patients died of disease. One patient was alive with no evidence of disease. Conclusions: Atypical EHE is a more aggressive tumor than classic EHE, with histological features including high nuclear grade, increased mitotic activity, the presence of solid growth pattern and tumor necrosis. The differential diagnoses include epithelioid angiosarcoma, carcinoma and epithelioid sarcoma.

OBJECTIVE

To study the clinicopathologic features and differential diagnosis of alveolar soft part sarcoma (ASPS).

METHODS

The clinical data and pathologic features of 48 cases of ASPS were evaluated. Immunohistochemical study, PAS staining and fluorescence in-situ hybridization (FISH) were carried out in selected examples. Relevant literature was reviewed.

RESULTS

Amongst the 48 cases studied, there were 17 males and 31 females, with male-to-female ratio of 1.0∶1.8. The age of patients ranged from 2 to 60 years (median=26 years). The tumor was most commonly located in deep soft tissue, especially that of lower extremities. Histologically, the tumor cells were arranged in alveolar or solid patterns and separated by sinusoidal vessels. They were large and contained abundant eosinophilic granules or crystals in cytoplasm. The nuclei were round to polygonal and vesicular, often with prominent nucleoli. Intravascular tumor extension was common. Some cases showed necrosis, hemorrhage and cystic changes. Immunohistochemical study showed that the tumor cells were positive for TFE3 (100%, 33/33). FISH assay was carried out in 4 cases and all of them had TFE3-ASPL gene fusion.

CONCLUSIONS

ASPS is a rare malignant neoplasm, often occurs in young patients. TFE3 is a useful immunohistochemical marker for diagnosis. The diagnosis is further confirmed by other markers.

Alveolar soft part sarcoma (ASPS) is a rare soft tissue tumor of unknown histogenesis generally characterized by the der(17)t(X;17)(p11.2;q25) translocation which results in the ASPSCR1-TFE3 gene fusion. Primary ASPS of the thyroid gland has not yet been reported. During oncology follow-up for breast cancer, a pulmonary nodule and thyroid gland mass were identified in a 71-year-old Korean male. Thyroid ultrasound showed a 5.7 cm left thyroid gland mass. After several fine needle aspirations, a thyroid gland lobectomy was performed after documenting only non-caseating granulomatous inflammation in a biopsy of the lung nodule. A 7.6 cm bulging nodular thyroid gland mass was identified, showing significant destructive invasion. Alveolar nests of large polygonal, eosinophilic, granular neoplastic cells were separated by vascularized stroma. Colloid was absent. Tumor necrosis and increased mitoses were identified. The neoplastic cells were positive with TFE3 and CD68, but negative with pancytokeratin, thyroglobulin, TTF-1, napsin-A, calcitonin, PAX8, CAIX, S100 protein, HMB45, SMA, and desmin. FISH confirmed a TFE3 gene rearrangement. The differential includes several primary thyroid gland epithelial neoplasms, paraganglioma, PEComa, melanoma, crystal storage disease, and metastatic carcinomas, especially Xp11 translocation renal cell carcinoma. The patient has refused additional therapy, but is alive without tumor identified (primary or metastatic).

Rationale: The ubiquitin-proteasome system (UPS) is responsible for skeletal muscle atrophy. We showed earlier that the transcription factor EB (TFEB) plays a role by increasing E3 ubiquitin ligase muscle really interesting new gene-finger 1(MuRF1)/tripartite motif-containing 63 (TRIM63) expression. MuRF 1 ubiquitinates structural proteins and mediates their UPS-dependent degradation. We now investigated how TFEB-mediated TRIM63 expression is regulated.

Objective: Because protein kinase D1 (PKD1), histone deacetylase 5 (HDAC5), and TFEB belong to respective families with close structural, regulatory, and functional properties, we hypothesized that these families comprise a network regulating TRIM63 expression.

Methods and results: We found that TFEB and transcription factor for immunoglobulin heavy-chain enhancer 3 (TFE3) activate TRIM63 expression. The class IIa HDACs HDAC4, HDAC5, and HDAC7 inhibited this activity. Furthermore, we could map the HDAC5 and TFE3 physical interaction. PKD1, PKD2, and PKD3 reversed the inhibitory effect of all tested class IIa HDACs toward TFEB and TFE3. PKD1 mediated nuclear export of all HDACs and lifted TFEB and TFE3 repression. We also mapped the PKD2 and HDAC5 interaction. We found that the inhibitory effect of PKD1 and PKD2 toward HDAC4, HDAC5, and HDAC7 was mediated by their phosphorylation and 14-3-3 mediated nuclear export.

Conclusion: TFEB and TFE3 activate TRIM63 expression. Both transcription factors are controlled by HDAC4, HDAC5, HDAC7, and all PKD-family members. We propose that the multilevel PKD/HDAC/TFEB/TFE3 network tightly controls TRIM63 expression.

Keywords: HDAC = histone deacetylase; TFE3; muscle atrophy; muscle ring finger protein 1; protein kinase D; transcription factor EB.

Alveolar soft part sarcoma, ASPS, is a rare malignant tumor, with preferential primary localization in limbs, usually occurring in adolescents and young adults. This sarcoma, well defined histologically and at molecular level, has an indolent course, but a high potential metastatic pulmonary and cerebral evolution, sometimes late. ASPS is characterized by an almost specific translocation t(X, 17)(p11;25) which creates a fusion protein, APSL-TFE3, acting as an aberrant transcription factor. An in-bloc resection of the primary tumor is the treatment of choice in cases of localized disease. Conventional chemotherapy is generally ineffective. The role of radiotherapy is discussed in case of micro- or macroscopical incomplete residue. It seems to reduce local recurrence, but did not influence overall survival. The 5 years survival rate in children, adolescents and young adults is close to 80% in case of localized disease but poorer in presence of metastases. Recently, systemic anti-tumoral treatments have been focused on the use of targeted therapies. Anti-angiogenic drugs and tyrosine kinase inhibitors are the most promising approaches, but require further study. Prognostic risk factors in the literature are age (>10Y), tumor size (>5cm) and presence of metastases. This article reviews the clinical manifestations, diagnosis modalities, radiographic characteristics and therapeutic strategy of this disease in the pediatric population.

Purpose of review: Alveolar soft part sarcoma (ASPS) represent 0.5% of sarcomas, defining a rarest among rare malignancies. It affects young adults, displaying slow-growing mass of the thigh, head and neck, and trunk. Although quite indolent, a majority of cases display an advanced disease with lung bone or central nervous system metastasis. Complete surgery is the cornerstone of localized ASPS, and advanced diseases poorly respond to chemotherapy. Here discuss recent progress in molecular characterization of ASPS and future prospects of therapeutic approaches.

Recent findings: ASPS is characterized by a specific oncogenic translocation ASPSCR1-TFE3 that induce hepatocyte growth factor receptor (MET) overexpression, angiogenesis, and immunosuppression in the tumor microenvironment. These specific biological features have encouraged the successful exploration of MET inhibitor, antiangiogenic drugs, and immunotherapy. We reviewed the main tracks of ASPS biology and recent insights from targeted therapies is ASPS mainly driven tyrosine kinase inhibitors (especially antiangiogenics), immune-checkpoint inhibitors, and their combinations.

Summary: Overall, antiangiogenics and anti Programmed cell death 1/Programmed cell death ligand 1 therapies showed a significant activity in ASPS that warrant additional investigation through randomized trials to validate those results and through ancillary biological studies to better understand resistance mechanisms and biomarkers of response.

Purpose of review: Alveolar soft part sarcoma (ASPS) represent 0.5% of sarcomas, defining a rarest among rare malignancies. It affects young adults, displaying slow-growing mass of the thigh, head and neck, and trunk. Although quite indolent, a majority of cases displays an advanced disease with lung bone or central nervous system metastasis. Complete surgery is the cornerstone of localized ASPS, and advanced diseases poorly respond to chemotherapy. Here discuss recent progress in molecular characterization of ASPS and future prospects of therapeutic approaches.

Recent findings: ASPS is characterized by a specific oncogenic translocation ASPSCR1-TFE3 that induce hepatocyte growth factor receptor (MET) overexpression, angiogenesis, and immunosuppression in the tumor microenvironment. These specific biological features have encouraged the successful exploration of MET inhibitors, antiangiogenic drugs, and immunotherapy. We reviewed the main tracks of ASPS biology and recent insights from targeted therapies is ASPS mainly driven tyrosine kinase inhibitors (especially antiangiogenics), immune-checkpoint inhibitors, and their combinations.

Summary: Overall, antiangiogenics and anti Programmed cell death 1/Programmed cell death ligand 1 therapies showed a significant activity in ASPS that warrants additional investigation through randomized trials to validate those results and through ancillary biological studies to better understand resistance mechanisms and biomarkers of response.

Xp11.2 translocation renal cell carcinomas are rare tumors characterized by translocations involving chromosome Xp11.2. These tumors are predominantly reported in pediatric patients. The authors report Xp11.2 translocation renal cell carcinoma in a 13-year-old girl who presented with asymptomatic palpable right renal mass. Right radical nephrectomy was performed and revealed a well-defined solid mass at the lower pole of the kidney. Microscopically, the tumor was composed of sheets and nests of clear to pale eosinophilic cells with some alveolar growth pattern. Psammoma bodies were detected. Immunohistochemically, the tumor cells marked with TFE3, focally marked with smooth muscle actin, HMB-45, CD68, progesterone receptor (PR) and CD10 but did not mark with epithelial markers (AE1/AE3, EMA and CAM5.2), vimentin, S-100 and p53. The presence of psammoma bodies is an important diagnostic clue for these tumors. Cytogenetic study and/or immunohistochemistry for TFE3 protein are needed for confirming the diagnosis. Currently, surgery seems to be the most effective therapy Pediatric patients with these tumors are believed to have a favorable prognosis.

Ossifying fibromyxoid tumor (OFMT) is a soft tissue tumor frequently displaying gene fusions, most of which affect the PHF1 gene. PHF1 encodes plant homeodomain finger protein 1, which is involved in various processes regulating gene transcription, including those orchestrated by the polycomb repressor complex 2. Here, a series of 37 OFMTs, including 18 typical, 9 atypical, and 10 malignant variants, was analyzed with regard to transcriptomic features, gene fusion and copy number status, and/or single-nucleotide variants. The effects on gene expression and chromatin accessibility of three detected fusions (EP400-PHF1, MEAF6-PHF1, and PHF1-TFE3) were further evaluated in fibroblasts. Genomic imbalances showed a progression-related pattern, with more extensive copy number changes among atypical/malignant lesions than among typical OFMTs; loss of the RB1 gene was restricted to atypical/malignant OFMTs, occurring in one-third of the cases. RNA sequencing identified fusion transcripts in >80% of the cases analyzed, including a novel CSMD1-MEAF6. The gene-expression profile of OFMT was distinct from that of other soft tissue tumors, with extensive transcriptional upregulation of genes in OFMT. These findings were largely recapitulated in gene fusion-expressing fibroblast lines, suggesting that genes involved in, e.g., Wnt signaling and/or being regulated through trimethylation of lysine 27 in histone 3 (H3K27me3) are pivotal for OFMT development. The genes showing differentially higher expression in fusion-expressing cells paralleled increased chromatin accessibility, as revealed by ATAC sequencing. Thus, the present study suggests that OFMT develops through gene fusions that have extensive epigenetic consequences.

OBJECTIVE

To investigate clinicopathological features, molecular genetic characteristics, differential diagnoses and prognosis of renal cell carcinoma in teenagers.

METHODS

Microscopic and immunohistochemical features of 46 cases of renal cell carcinomas in teenagers were reviewed along with the clinical follow-up data. Loss of heterozygosity (LOH), analysis of von Hippel-Lindau (VHL) gene and screening for VHL gene mutations were performed in all of the tumors.

RESULTS

There were 19 Xp11.2 translocations/TFE3 gene fusions renal clear cell carcinomas (Xp11 RCCs), 9 chromophobe renal cell carcinomas (CCRCCs), 17 papillary renal cell carcinomas (PRCCs), and 1 unclassified renal cell carcinoma (RCC). All of the 19 Xp11.2 translocation RCCs showed a moderate to strong immunoreactivity for TFE, however, no TFEB expression was obtained. There were 4 histological patterns in the Xp11 RCC cases including: 8 tumors possessing a nested to papillary architecture resembling to the t(X;17) ASPL-TFE3 phenotype; 6 tumors possessing a morphologic feature like the t(X;1) PRCC-TFE3 phenotype; 4 cases morphologically resembling to clear cell RCC; and 1 Xp11 RCC case, with a special morphologic feature not searched yet in the literature, including a ground glass appearance of the nuclei accompanying occasionally with grooves on the nuclear surface; nucleoli inconspicuous with accumulation of abundant mucin-like substance in the stroma. VHL gene analysis revealed deletions at 3p25-26 in one clear cell RCC and one papillary type 2 RCC. The papillary type 2 RCC had also a family history of VHL disease, with a germline G→C mutation at a splicing site of position 553+5. There were no VHL mutations detected in the remaining 45 RCCs. Statistical analysis of tumor stage and outcome revealed that TFE+ RCCs of teen-agers were more frequently associated with a higher pT3/pT4 stage and a poorer outcome than that of the TFE-RCCs (P < 0.05).

CONCLUSIONS

RCCs of the teenagers have a different morphologic spectrum and genetic background from the RCCs seen in adults. Among RCCs of the teen-agers, Xp11.2 translocation tumors are the most common RCCs and have a poorer prognosis than that of the TFE-RCCs.