Melanotic Xp11 translocation renal cancers: a distinctive neoplasm with overlapping features of PEComa, carcinoma, and melanoma. Am J Surg Pathol. 2009;33:609-619. [PMID: 19065101 DOI: 10.1097/pas.0b013e31818fbdff]

Translocation Renal Cell Carcinoma: An Update on Clinicopathological and Molecular Features

Microphthalmia-associated transcription (MiT) family translocation renal cell carcinoma (tRCC) comprises Xp11 tRCC and t(6;11) RCC. Due to the presence of fusion genes, Xp11 tRCC and t(6;11) RCC are also known as TFE3- and TFEB-rearranged RCC, respectively. TFE3 and TFEB belong to the MiT family, which regulates melanocyte and osteoclast differentiation, and TFE3- and TFEB-rearranged RCC show characteristic clinicopathological and immunohistochemical features. Recent studies identified the fusion partner-dependent clinicopathological and immunohistochemical features in TFE3-rearranged RCC. Furthermore, RCC with chromosome 6p amplification, including TFEB, was identified as a unique subtype of RCC, along with ALK-rearranged RCC. This review summarizes these recent advancements in our tRCC-related knowledge.

Melanotic MiT family translocation neoplasms: Expanding the clinical and molecular spectrum of this unique entity of tumors

MiT family translocation tumors are a group of neoplasms characterized by translocations involving MiT family transcription factors. The translocation renal cell carcinomas, TFE3 (Xp11.2) and TFEB (t6;11) are known members of this family. Melanotic Xp11 translocation renal cancer is a more recently described entity. To date only 14 cases have been described. It is characterized by a distinct set of features including a nested epithelioid morphology, melanin pigmentation, labeling for markers of melanocytic differentiation, lack of labeling for markers of renal tubular differentiation, predominance in a younger age population and association with aggressive clinical behavior. There are noted similarities between that entity and TFE3 associated PEComas. There are no cases reported of equivalent melanotic TFEB translocation renal cancer. We report 2 rare cases of melanotic translocation renal neoplasms. The first is a melanotic TFE3 translocation renal cancer with an indolent clinical course, occurring in a patient more than 3-decades older than the usual average age in which such tumors have been described. The other case is, to our knowledge, the first reported melanotic TFEB translocation cancer of the kidney. Both cases exhibit the same H&E morphology as previously reported in melanotic translocation renal cancers and label accordingly with HMB45 and Melan-A. While the TFE3 melanotic tumor lacked any evidence of renal tubular differentiation, the TFEB melanotic cancer exhibited some staining for renal tubular markers. Based on the unique features noted above, these two cases expand the clinical and molecular spectrum of the melanotic translocation renal cancers.

TFE3-Fusion Variant Analysis Defines Specific Clinicopathologic Associations Among Xp11 Translocation Cancers

Xp11 translocation cancers include Xp11 translocation renal cell carcinoma (RCC), Xp11 translocation perivascular epithelioid cell tumor (PEComa), and melanotic Xp11 translocation renal cancer. In Xp11 translocation cancers, oncogenic activation of TFE3 is driven by the fusion of TFE3 with a number of different gene partners; however, the impact of individual fusion variant on specific clinicopathologic features of Xp11 translocation cancers has not been well defined. In this study, we analyze 60 Xp11 translocation cancers by fluorescence in situ hybridization using custom bacterial artificial chromosome probes to establish their TFE3 fusion gene partner. In 5 cases RNA sequencing was also used to further characterize the fusion transcripts. The 60 Xp11 translocation cancers included 47 Xp11 translocation RCC, 8 Xp11 translocation PEComas, and 5 melanotic Xp11 translocation renal cancers. A fusion partner was identified in 53/60 (88%) cases, including 18 SFPQ (PSF), 16 PRCC, 12 ASPSCR1 (ASPL), 6 NONO, and 1 DVL2. We provide the first morphologic description of the NONO-TFE3 RCC, which frequently demonstrates subnuclear vacuoles leading to distinctive suprabasal nuclear palisading. Similar subnuclear vacuolization was also characteristic of SFPQ-TFE3 RCC, creating overlapping features with clear cell papillary RCC. We also describe the first RCC with a DVL2-TFE3 gene fusion, in addition to an extrarenal pigmented PEComa with a NONO-TFE3 gene fusion. Furthermore, among neoplasms with the SFPQ-TFE3, NONO-TFE3, DVL2-TFE3, and ASPL-TFE3 gene fusions, the RCCs are almost always PAX8 positive, cathepsin K negative by immunohistochemistry, whereas the mesenchymal counterparts (Xp11 translocation PEComas, melanotic Xp11 translocation renal cancers, and alveolar soft part sarcoma) are PAX8 negative, cathepsin K positive. These findings support the concept that despite an identical gene fusion, the RCCs are distinct from the corresponding mesenchymal neoplasms, perhaps due to the cellular context in which the translocation occurs. We corroborate prior data showing that the PRCC-TFE3 RCCs are the only known Xp11 translocation RCC molecular subtype that are consistently cathepsin K positive. In summary, our data expand further the clinicopathologic features of cancers with specific TFE3 gene fusions and should allow for more meaningful clinicopathologic associations to be drawn.

Postoperative recurrence of adult renal cell carcinoma associated with Xp11.2 translocation/TFE3 gene fusion

Objective

To analyze the postoperative recurrence of renal cell carcinoma associated with Xp11.2 translocation/TFE3 gene fusion (Xp11.2 tRCC).

Methods

This retrospective study was approved by the institutional review board and performed in accordance with the ethical standards established by the institution. Demographic, clinical, pathological, and follow-up data were compiled for the study cohort.

Results

During a mean follow-up of 41.3 months (range, 3–104 months), 8 of 34 patients with Xp11.2 tRCC were confirmed to have recurrence. Three of these patients died with poor outcomes due to a vena cava tumor embolus, and one died of distant metastasis 48 months after the initial nephrectomy during which lymph node metastasis was found. Three patients survived after cytoreduction surgery. One patient was diagnosed with lung metastasis 11 months postoperatively.

Conclusions

The TNM classification provides significant prognostic information for Xp11.2 tRCC. A relatively active surveillance algorithm is recommended, and cytoreduction surgery is an effective approach for recurrent Xp11.2 tRCC. Larger studies are required to more extensively investigate the recurrence of these potentially aggressive tumors.

Alveolar Soft Part Sarcoma of the Female Genital Tract: A Morphologic, Immunohistochemical, and Molecular Cytogenetic Study of 10 Cases With Emphasis on its Distinction From Morphologic Mimics

Alveolar soft part sarcoma (ASPS) is a morphologically distinctive neoplasm of unknown differentiation that bears a characteristic gene fusion involving ASPSCR1 and TFE3. ASPS can occur in the female genital tract, but is rare. Eleven cases with an initial diagnosis of ASPS at female genital tract sites were evaluated for their morphologic features and immunoprofile using a panel of antibodies (TFE3, HMB45, melan-A, smooth muscle actin, desmin, and h-Caldesmon). In addition, the presence of TFE3 rearrangement and subsequent ASPSCR1-TFE3 fusion were determined by fluorescence in situ hybridization. Ten tumors retained their classification as ASPS based on their morphologic appearance, immunohistochemical profile, and demonstration of ASPSCR1-TFE3 fusion. The remaining case was reclassified as conventional-type PEComa due to its pattern of HMB45, melan-A, and desmin positivity as well as absence of TFE3 rearrangement. Sites of the 10 ASPS were uterine corpus (3), cervix (2), uterus not further specified (2), vagina (2), and vulva (1). The age of the patients ranged from 15 to 68 years (mean 34 y, median 32 y). The tumors demonstrated a spectrum of morphologic features, but all had a consistent immunophenotype of strong TFE3 nuclear expression and lack of muscle (smooth muscle actin, desmin, h-Caldesmon) and melanocytic (melan-A, HMB45) markers, except focal positivity for HMB45 in 1. Follow-up was available for 4 patients ranging from 1 to 35 months (mean 15 mo, median 25 mo) and they were alive and had no evidence of recurrence or metastasis at last follow-up. Distinguishing ASPS from its morphologic mimics, particularly PEComa, is important due to increasingly efficacious targeted agents such as MET-selective and VEGF signaling inhibitors in the former and mTOR inhibition therapy in the latter.

SFPQ/PSF-TFE3 renal cell carcinoma: a clinicopathologic study emphasizing extended morphology and reviewing the differences between SFPQ-TFE3 RCC and the corresponding mesenchymal neoplasm despite an identical gene fusion

Xp11 translocation renal cell carcinoma (RCC) with SFPQ/PSF-TFE3 gene fusion is a rare epithelial tumor. Of note, the appearance of the gene fusion does not necessarily mean that it is renal cell carcinoma. The corresponding mesenchymal neoplasms, including Xp11 neoplasm with melanocytic differentiation, TFE3 rearrangement-associated perivascular epithelioid cell tumor (PEComa) and melanotic Xp11 translocation renal cancer, can also harbor the identical gene fusion. However, the differences between Xp11 translocation RCC and the corresponding mesenchymal neoplasm have only recently been described. Herein, we examined 5 additional cases of SFPQ-TFE3 RCCs using clinicopathologic, immunohistochemical, and molecular analyses. One tumor had the typical morphologic features of SFPQ-TFE3 RCC, whereas other 3 cases demonstrated the unusual morphologic features associated with pseudorosettes formation or clusters of smaller cells, mimicking TFEB RCC. The remaining one showed branching tubules and papillary structure composed of clear and eosinophilic tumor cells. Immunohistochemically, all 5 cases demonstrated moderate (2+) or strong (3+) positive staining for TFE3, PAX-8 and CD10, whereas no cases demonstrated TFEB, Cathepsin K, CA-IX, CK7, Melan-A, or HMB-45 expression. Genetically, the fusion transcripts were identified in 3 cases by reverse-transcription polymerase chain reaction (RT-PCR). On the basis of fluorescence in situ hybridization (FISH) analysis, all the cases were detected with SFPQ-TFE3 gene fusion. Clinical follow-up data were available for all the patients, and no one developed tumor recurrence, progression, or metastasis. We also review the differences between SFPQ-TFE3 RCC and the corresponding mesenchymal neoplasm despite the identical gene fusion. The presence of pseudorosettes also expands the known histological features of SFPQ-TFE3 RCC.

TFE3-Expressing Perivascular Epithelioid Cell Neoplasm (PEComa) of the Sella Turcica

We report a primary central nervous system (CNS) perivascular epithelioid cell tumor (PEComa) in a middle-aged female patient. The tumor occurred in suprasellar location with secondary extension into the sella turcica. The patient presented with intracranial hemorrhage and an altered level of consciousness. The tumor had morphologic features matching those of other previously described TFE3-translocated PEComas, including epithelioid morphology, diffuse and strong nuclear immunoreactivity for TFE3, and minimal staining with myoid markers. The TFE3 break-apart FISH testing showed a slight splitting of one of the TFE3 signals in 49.5 % of nuclei. This case illustrates that PEComas should be added to the growing list of mesenchymal tumors that can be encountered in the CNS and specifically in the vicinity of the pituitary gland. The recognition of this entity is of significance given their underlying pathogenesis and possible management implications.

[The translocation carcinoma: A pediatric renal tumor also in adults]

The MiT family of translocation-associated renal cell carcinomas comprise approximately 40 % of renal cell carcinomas in young patients but only up to 4 % of renal cell carcinomas in adult patients. The Xp11.2 translocation-associated tumors are the most frequent and were included in the 2004 World Health Organization (WHO) classification. They contain a fusion of the TFE3 gene with ASPSCR1, PRCC, NONO, SPFQ or CLTC resulting in an immunohistochemically detectable nuclear overexpression of TFE3. The Xp11.2 translocation-associated renal cell carcinomas are characterized by ample clear cytoplasm, papillary architecture and abundant psammoma bodies. The TFEB translocation-associated renal cell carcinomas are much rarer and show a biphasic architecture. Fluorescence in situ hybridization permits the detection of a translocation by means of a break apart probe for the TFE3 and TFEB genes and is recommended for the diagnosis of renal cell carcinomas in patients under 30 years of age. The TFE3 and TFEB translocation-associated tumors are classified as MiT family translocation carcinomas in the new WHO classification.The rare renal cell carcinomas harboring an ALK rearrangement with fusion to VCL in young patients with sickle cell trait show a characteristic morphology and are listed in the new WHO classification as a provisional entity.

Melanotic Xp11 Translocation Renal Cancer Managed With Radical Nephrectomy and IVC Tumor Thrombectomy

Melanotic Xp11 translocation renal cancer is a rarely observed neoplasm primarily affecting adolescents and young adults. Given the paucity of data describing this malignancy, its natural history and subsequent long-term management are not well understood. We report a case of melanotic Xp11 translocation with tumor thrombus extension managed with radical nephrectomy and inferior vena cava (IVC) tumor thrombectomy. To our knowledge, this is the first case report to describe use of conventional tumor thrombectomy techniques in a patient with melanotic Xp11 translocation renal cancer.

An Xp11.2 translocation renal cell carcinoma with SMARCB1 (INI1) inactivation in adult end-stage renal disease: a case report

BACKGROUND

Xp11.2 translocation/transcription factor E3 (TFE3) rearrangement renal cell carcinoma (RCC) is a rare subtype of RCC with limited clinical and pathological data.

CASE PRESENTATION

Here we present an unusual high-grade Xp11.2 translocation RCC with a rhabdoid feature and SMARCB1 (INI1) inactivation in a 40-year-old man with end-stage kidney disease. The histological examination of the dissected left renal tumor showed an organoid architecture of the eosinophilic or clear neoplastic cells with necrosis and high mitotic activity. In some areas, non-adhesive tumor cells with eccentric nuclei were observed. Immunohistochemically (IHC), the tumor cells are positive for TFE3 and the renal tubular markers (PAX2 and PAX8), and completely negative for SMARCB1, an oncosuppressor protein. Break-apart florescence in situ hybridization and reverse transcription polymerase chain reaction confirmed TFE3 rearrangement on Xp11.2 and the presence of ASPSCR1-TFE3 fusion gene. DNA sequencing revealed a frameshift mutation in exon 4 of SMARCB1 gene.

CONCLUSION

It is important to recognize this rare RCC with both TFE3 rearrangement and SMARCB1 inactivation, as the prognosis and therapeutic strategies, particularly targeted therapies for such tumors, might be different.

Primary Malignant Melanoma of Renal Pelvis with Extensive Clear Cell Change

Our presentation illustrates a rare case of primary renal pelvis malignant melanoma in a 35-year-old man. The diagnosis of malignant melanoma was based on immunophenotype and the detection of intracellular melanin pigment. The renal origin was proven by the presence of scattered melanocytes within the urothelium of the pelvis. The tumor exhibited extensive clear cell change that closely mimics clear cell renal cell carcinoma. The patient's clinical history did not disclose any signs of previous melanocytic skin or mucosa lesions. Differential diagnosis includes tumors capable of synthesizing melanin or expressing melanocytic markers.

Identification by FFPE RNA-Seq of a new recurrent inversion leading to RBM10-TFE3 fusion in renal cell carcinoma with subtle TFE3 break-apart FISH pattern

Gene fusions involving TFE3 defines the "Xp11.2 translocations" subclass of renal cell carcinomas (RCCs) belonging to the MiT family translocation RCC. Four recurrent TFE3 fusion partners were identified to date: PRCC, ASPSCR1, SFPQ, and NONO. Break-apart TFE3 fluorescence in situ hybridization (FISH) on formalin-fixed and paraffin-embedded (FFPE) tissue sections is currently the gold standard for identification of TFE3 rearrangements. Herein, we report a case of RCC with a morphological appearance of Xp11.2 translocation, and positive TFE3 immunostaining. By FISH, the spots constituting the split signal were barely spaced, suggestive of a chromosome X inversion rather than a translocation. We performed RNA-seq from FFPE material to test this hypothesis. RNA-seq suggested a fusion of RBM10 gene exon 17 (Xp11.23) with TFE3 gene exon 5 (Xp11.2). RBM10-TFE3 fusion transcript was confirmed using specific RT-PCR. Our work showed that RNA-Seq is a robust technique to detect fusion transcripts from FFPE material. A RBM10-TFE3 fusion was previously described in single case of Xp11.2 RCC. Although rare, RBM10-TFE3 fusion variant (from chromosome X paracentric inversion), therefore, appears to be a recurrent molecular event in Xp11.2 RCCs. RBM10-TFE3 fusion should be added in the list of screened fusion transcripts in targeted molecular diagnostic multiplex RT-PCR. © 2016 Wiley Periodicals, Inc.

Xp11 neoplasm with melanocytic differentiation of the prostate harbouring the novel NONO-TFE3 gene fusion: report of a unique case expanding the gene fusion spectrum

Recently, an increasing number of TFE3 rearrangement-associated tumours have been reported, such as TFE3 rearrangement-associated perivascular epithelioid cell tumours (PEComas), melanotic Xp11 translocation renal cancers and melanotic Xp11 neoplasms. We have suggested that these tumours belong to a single clinicopathological spectrum. 'Xp11 neoplasm with melanocytic differentiation' or 'melanotic Xp11 neoplasm' have been proposed to designate this unique neoplasm. Herein, we describe the first case of an Xp11 neoplasm with melanocytic differentiation to be described in the prostate, bearing the novel NONO-TFE3 gene fusion. This study both adds to the spectrum regarding melanotic Xp11 neoplasms and expands its gene fusion spectrum. Moreover, we discuss the relationship of these rare tumours to neoplasms such as conventional PEComas, alveolar soft part sarcomas, malignant melanomas, clear cell sarcomas and Xp11 translocation renal cancers.

MiT Family Translocation-Associated Renal Cell Carcinoma: A Contemporary Update With Emphasis on Morphologic, Immunophenotypic, and Molecular Mimics

Translocation-associated renal cell carcinoma (t-RCC) is a relatively uncommon subtype of renal cell carcinoma characterized by recurrent gene rearrangements involving the TFE3 or TFEB loci. TFE3 and TFEB are members of the microphthalmia transcription factor (MiT) family, which regulates differentiation in melanocytes and osteoclasts, and MiT family gene fusions activate unique molecular programs that can be detected immunohistochemically. Although the overall clinical behavior of t-RCC is variable, emerging molecular data suggest the possibility of targeted approaches to advanced disease. Thus, distinguishing t-RCC from its morphologic, immunophenotypic, and molecular mimics may have important clinical implications. The differential diagnosis for t-RCC includes a variety of common renal neoplasms, particularly those demonstrating clear cell and papillary features; in addition, because of immunophenotypic overlap and/or shared molecular abnormalities (ie, TFE3 gene rearrangement), a distinctive set of nonepithelial renal tumors may also warrant consideration. Directed ancillary testing is an essential aspect to the workup of t-RCC cases and may include a panel of immunohistochemical stains, such as PAX8, pancytokeratins, epithelial membrane antigen, carbonic anhydrase IX, HMB-45, and Melan-A. Dual-color, break-apart fluorescent in situ hybridization for TFE3 or TFEB gene rearrangement may be helpful in diagnostically challenging cases or when molecular confirmation is needed.

Unsuspected Xp11 Translocation Renal Neoplasm Associated With Contralateral Clear Cell Carcinoma

In this report, we present for the first time the coexistence of a conventional renal cell carcinoma (RCC) and an undefined Xp11 translocation renal neoplasm in distinct kidneys, which was difficult to definitively classify as either carcinoma or PEComa (perivascular epithelioid cell tumor). While one of the tumors showed the morphological and immunohistochemical features of clear RCC, the other had an unusual morphology with a prominent nested pattern. Microscopically this tumor showed nests of cells with clear and eosinophilic cytoplasm and nuclei with prominent nucleoli; some hyaline globules were evident. Immunohistochemical panel showed negativity for cytokeratin-pan, cytokeratin-7, PAX8, and CD10 but positive immunostaining for cathepsin K, racemase, Melan-A, and TFE3. A subsequent, metaphase, dual-color fluorescence in situ hybridization confirmed the Xp11 translocation. Attention should be paid to the routine immunohistochemical profile that, in case of negativity of specific RCC markers, may suggest an Xp11 translocation renal tumor. The addition of TFE3 can easily identify the specific subtype.

PSF/SFPQ is a very common gene fusion partner in TFE3 rearrangement-associated perivascular epithelioid cell tumors (PEComas) and melanotic Xp11 translocation renal cancers: clinicopathologic, immunohistochemical, and molecular characteristics suggesting classification as a distinct entity

An increasing number of TFE3 rearrangement-associated tumors, such as TFE3 rearrangement-associated perivascular epithelioid cell tumors (PEComas), melanotic Xp11 translocation renal cancers, and melanotic Xp11 neoplasms, have recently been reported. We examined 12 such cases, including 5 TFE3 rearrangement-associated PEComas located in the pancreas, cervix, or pelvis and 7 melanotic Xp11 translocation renal cancers, using clinicopathologic, immunohistochemical, and molecular analyses. All the tumors shared a similar morphology, including a purely nested or sheet-like architecture separated by a delicate vascular network, purely epithelioid cells displaying a clear or granular eosinophilic cytoplasm, a lack of papillary structures and spindle cell or fat components, uniform round or oval nuclei containing small visible nucleoli, and, in most cases (11/12), melanin pigmentation. The levels of mitotic activity and necrosis varied. All 12 cases displayed moderately (2+) or strongly (3+) positive immunoreactivity for TFE3 and cathepsin K. One case labeled focally for HMB45 and Melan-A, whereas the others typically labeled moderately (2+) or strongly (3+) for 1 of these markers. None of the cases were immunoreactive for smooth muscle actin, desmin, CKpan, S100, or PAX8. PSF-TFE3 fusion genes were confirmed by reverse transcription polymerase chain reaction in cases (7/7) in which a novel PSF-TFE3 fusion point was identified. All of the cases displayed TFE3 rearrangement associated with Xp11 translocation. Furthermore, we developed a PSF-TFE3 fusion fluorescence in situ hybridization assay for the detection of the PSF-TFE3 fusion gene and detected it in all 12 cases. Clinical follow-up data were available for 7 patients. Three patients died, and 2 patients (cases 1 and 3) remained alive with no evidence of disease after initial resection. Case 2 experienced recurrence and remained alive with disease. Case 5, a recent case, remained alive with extensive abdominal cavity metastases. Our data suggest that these tumors belong to a single clinicopathologic spectrum and expand the known characteristics of TFE3 rearrangement-associated tumors.

Validation and utilization of a TFE3 break-apart FISH assay for Xp11.2 translocation renal cell carcinoma and alveolar soft part sarcoma

Background

Xp11.2 or TFE3 translocation renal cell carcinomas (RCC) and alveolar soft part sarcoma (ASPS) are characterized by chromosome translocations involving the Xp11.2 breakpoint resulting in transcription factor TFE3 gene fusions. The most common translocations documented in TFE3 RCCs are t(X;1) (p11.2;q21) and t(X;17) (p11.2;q25) which leads to fusion of TFE3 gene on Xp11.2 with PRCC or ASPL respectively. TFE3 immunohistochemistry (IHC) has been inconsistent over time due to background staining problems in part related to fixation issues. Karyotyping to detect TFE3 gene rearrangement requires typically unavailable fresh tissue. Reverse transcriptase-polymerase chain reaction (RT-PCR) is generally very challenging due to degradation of RNA in archival material. The study objective was to develop and validate a TFE3 break-apart fluorescence in situ hybridization (FISH) assay to confirm Xp11 translocation RCCs and ASPS.

Methods

Representative sections of formalin-fixed paraffin-embedded tissue blocks were selected in 40 possible cases. Approximately 60 tumor cells were analyzed in the targeted region. The validation of TFE3 FISH was done with 11 negative and two positive cases. Cut off for a positive result was validated as >7.15 % positive nuclei with any pattern of break-apart signals. FISH evaluation was done blinded of the immunohistochemical or karyotype data.

Results

Three out of forty cases were positive for the TFE3 break-apart signals by FISH. The negative cases were reported as clear cell RCC with papillary features (10), clear cell RCC with sarcomatoid areas (2), Papillary RCC with clear cell areas (9), Chromophobe RCC (2), RCC, unclassified type (3) and renal medullary carcinoma (1). 3 of the negative cases were consultation cases for renal tumor with unknown histology. Seven negative cases were soft tissue tumor suspicious for ASPS.

Conclusion

Our study validates the utility of TFE3 break-apart FISH on formalin-fixed paraffin-embedded tissue sections for diagnosis and confirmation of Xp11.2 translocation RCCs and ASPS.

Alveolar soft part sarcoma of lung: report of a unique case with emphasis on diagnostic utility of molecular genetic analysis for TFE3 gene rearrangement and immunohistochemistry for TFE3 antigen expression

Alveolar soft part sarcoma (ASPS) is a rare, malignant mesenchymal tumor of distinctive clinical, morphologic, ultrastructural, and cytogenetical characteristics. It typically arises in the extremities of adolescents and young adults, but has also been documented in a number of unusual sites, thus causing diagnostic confusions both clinically and morphologically. The molecular signature of ASPS is a specific der(17)t(X;17)(p11.2;q25) translocation, which results in the fusion of TFE3 transcription factor gene at Xp11.2 with ASPL at 17q25. Recent studies have shown that the ASPL-TFE3 fusion transcript can be identified by reverse-transcriptase polymerase chain reaction analysis and TFE3 gene rearragement can be detected using a dual-color, break apart fluorescence in situ hybridization assay in paraffin-embedded tissue, and the resultant fusion protein can be detected immunohistochemically with antibody directed to the carboxy terminal portion of TFE3. Herein, we report a unique case of ASPS presenting as an asymptomatic mass in the lung of a 48 year-old woman without evidence of a primary soft tissue tumor elsewhere at the time of initial diagnosis. To the best of our knowledge, this is the third report of such cases appearing in the English language literature to date. We emphasize the differential diagnoses engendered by ASPS including a series of tumors involving the lung that have nested and alveolar growth patterns, and both clear and eosinophilic cytoplasm, and demonstrate the utility of molecular genetic analysis for TFE3 rearrangement and immunohistochemistry for TFE3 antigen expression for arriving at accurate diagnosis.

PEComa: morphology and genetics of a complex tumor family

Perivascular epithelioid cell tumors, or PEComas, are mesenchymal neoplasms composed of histologically and immunohistochemically distinctive epithelioid or spindle cells, which are immunoreactive for both smooth muscle and melanocytic markers. The cells in PEComas are typically arranged around blood vessels and appear to form the vessel wall, often infiltrating the smooth muscle of small- to medium-sized vessels. Periluminal cells are usually epithelioid and the more peripheral cells are spindle shaped. The cells have small, round to oval nuclei, sometimes with focal nuclear atypia, and clear to eosinophilic cytoplasm, and no counterpart normal cell has been identified. The PEComa "family" now includes angiomyolipoma, pulmonary clear cell "sugar" tumor and lymphangioleiomyomatosis, primary extrapulmonary sugar tumor, clear cell myomelanocytic tumor of the falciform ligament/ligamentum teres, abdominopelvic sarcoma of perivascular epithelioid cells, and other tumors with similar features at various sites that are simply termed PEComa. Some PEComas occur in patients with tuberous sclerosis complex and share the genetic abnormalities. There is a behavioral spectrum from benign to frankly malignant, and histologic criteria have been proposed for assessing malignant potential. The differential diagnosis can include carcinomas, smooth muscle tumors, other clear cell neoplasms, and adipocytic tumors. PEComas constitute a genetically diverse group that includes neoplasms harboring TFE3 gene rearrangements and those with TSC2 mutations, indicating alternative tumorigenic pathways. Recent advances in therapy of malignant PEComas relate to increased knowledge of specific genetic changes and their effects on metabolic pathways that are susceptible to specific interventions. We review PEComas, emphasizing the diagnostic spectrum and recent immunohistochemical and genetic findings.

An update on the application of newly described immunohistochemical markers in soft tissue pathology

CONTEXT

During the last 5 to 10 years, significant progress has been made in the molecular characterization of soft tissue tumors, predominantly with the identification of recurrent translocations or amplification of certain genes in different tumor types. Alongside this, translational efforts have identified many novel and diagnostically useful immunohistochemical markers for many of these tumor types.

OBJECTIVE

This article reviews a select group of recently described immunohistochemical markers of particular use in the evaluation of mesenchymal neoplasms; the underlying biology of the protein product, practical utility, and limitations of each marker are discussed in detail.

DATA SOURCES

Literature review, authors' research data, and personal practice experience serve as sources.

CONCLUSIONS

There are many diagnostically useful immunohistochemical markers to help confirm the diagnosis of many different soft tissue tumor types, some of which have reduced the need for additional, and more costly, studies, such as fluorescence in situ hybridization. However, no one marker is 100% specific for a given tumor, and knowledge of potential pitfalls and overlap in patterns of staining among other tumor types is crucial to ensure the appropriate application of these markers in clinical practice.

TFE3 translocation-associated perivascular epithelioid cell neoplasm (PEComa) of the gynecologic tract: morphology, immunophenotype, differential diagnosis

TFE3 translocation-associated PEComa is a distinct form of perivascular epithelioid cell neoplasm, the features of which are poorly defined owing to their general infrequency and limited prior reports with confirmed rearrangement or fusion. Recent investigation has found a lack of TSC gene mutation in these tumors compared with their nonrearranged counterparts, which underscores the importance of recognizing the translocated variant because of hypothetical ineffectiveness of targeted mTOR inhibitor therapy. Six cases were identified, and TFE3 rearrangement was confirmed by fluorescence in situ hybridization. Patient age ranged from 46 to 66 years (median 50 y), and none had a history of a tuberous sclerosis complex. Three cases arose in the uterine corpus, 1 in the vagina, 1 pelvic tumor, and 1 pulmonary tumor that was likely a recurrence/metastasis from a probable uterine primary. Five cases had clear cell epithelioid morphology that showed a spectrum of atypia, while 1 case had a mixture of clear cell epithelioid and spindle cells. A mostly consistent immunophenotype was observed in the clear cell epithelioid cases: each demonstrated diffuse TFE3, HMB45, cathepsinK labeling, either focal or no melanA staining, and variably weak reactivity to smooth muscle markers. The mixed clear cell epithelioid and spindle cell case had a similar expression pattern in its epithelioid component but strong muscle marker positivity in its spindle cell component. Follow-up ranged from 1 to 57 months. Three cases demonstrated aggressive behavior, and 3 cases had no evidence of recurrence. Both GYN-specific and traditional sets of criteria for malignancy were evaluated. The GYN model showed improved inclusion and specificity in comparison to the traditional model.

MiT family translocation renal cell carcinoma

The MiT subfamily of transcription factors includes TFE3, TFEB, TFC, and MiTF. Gene fusions involving two of these transcription factors have been identified in renal cell carcinoma (RCC). The Xp11 translocation RCCs were first officially recognized in the 2004 WHO renal tumor classification, and harbor gene fusions involving TFE3. The t(6;11) RCCs harbor a specific Alpha-TFEB gene fusion and were first officially recognized in the 2013 International Society of Urologic Pathology (ISUP) Vancouver classification of renal neoplasia. These two subtypes of translocation RCC have many similarities. Both were initially described in and disproportionately involve young patients, though adult translocation RCC may overall outnumber pediatric cases. Both often have unusual and distinctive morphologies; the Xp11 translocation RCCs frequently have clear cells with papillary architecture and abundant psammomatous bodies, while the t(6;11) RCCs frequently have a biphasic appearance with both large and small epithelioid cells and nodules of basement membrane material. However, the morphology of these two neoplasms can overlap, with one mimicking the other. Both of these RCCs underexpress epithelial immunohistochemical markers like cytokeratin and epithelial membrane antigen (EMA) relative to most other RCCs. Unlike other RCCs, both frequently express the cysteine protease cathepsin k and often express melanocytic markers like HMB45 and Melan A. Finally, TFE3 and TFEB have overlapping functional activity as these two transcription factors frequently heterodimerize and bind to the same targets. Therefore, on the basis of clinical, morphologic, immunohistochemical, and genetic similarities, the 2013 ISUP Vancouver classification of renal neoplasia grouped these two neoplasms together under the heading of "MiT family translocation RCC." This review summarizes our current knowledge of these recently described RCCs.

A case of PSF-TFE3 gene fusion in Xp11.2 renal cell carcinoma with melanotic features

Xp11.2 translocation renal cell carcinoma (Xp11.2 RCC) with PSF-TFE3 gene fusion is a rare neoplasm. Only 22 cases of Xp11.2 RCCs with PSF-TFE3 have been reported to date. We describe an additional case of Xp11.2 RCC with PSF-TFE3 showing melanotic features. Microscopically, the histologic features mimic clear cell renal cell carcinoma. However, the dark-brown pigments were identified and could be demonstrated as melanins. Immunohistochemically, the tumor cells were widely positive for CD10, human melanoma black 45, and TFE3 but negative for cytokeratins, vimentin, Melan-A, microphthalmia-associated transcription factor, smooth muscle actin, and S-100 protein. Genetically, we demonstrated PSF-TFE3 fusion between exon 9 of PSF and exon 5 of TFE3. The patient was free of disease with 50 months of follow-up. The prognosis of this type of tumor requires more cases because of limited number of cases and follow-up period. Xp11.2 RCC with PSF-TFE3 inevitably requires differentiation from other kidney neoplasms. Immunohistochemical and molecular genetic analyses are essential for accurate diagnosis.

Melanotic Xp11 translocation renal cancer: report of a case with a unique intratumoral sarcoid-like reaction

Background

Melanotic Xp11 translocation renal cancer is a rare tumor belonging to the family of microphthalmia-associated transcription factor (MiTF)/transcription factor E (TFE) neoplasms. This tumor family also includes alveolar soft part sarcoma, perivascular epithelioid cell neoplasms, Xp11 translocation renal cell carcinoma, and melanoma. To date, six confirmed melanotic Xp11 translocation cancers (five renal, one ovarian) have been reported in the literature.

Case Report

Here, we report the clinical, histologic, immunohistochemical, and molecular features of a unique melanotic Xp11 translocation renal cancer arising in a 34-year-old African-American female. Histologically, the tumor was composed of epithelioid tumor cells arranged in a nested pattern. The cells had clear to eosinophilic granular cytoplasm, vesicular nuclear chromatin, and prominent nucleoli. Multifocal intracytoplasmic deposits of granular brown melanin pigment were identified and confirmed by Fontana-Masson stain. An unusual histologic feature, not previously reported in melanotic Xp11 translocation renal cancer, was a sarcoid-like granulomatous reaction consisting of tight epithelioid granulomas with lymphocytic cuffing, numerous giant cells, and calcifications. Nuclear transcription factor E3 expression was identified by immunohistochemistry and TFE3 rearrangement was confirmed by fluorescence in situ hybridization. Additional immunohistochemical findings included immunoreactivity for HMB45, cathepsin K, and progesterone receptor; negative staining was seen with actin, desmin, cytokeratins, epithelial membrane antigen, CD10, vimentin, and PAX-8. The patient is currently free of disease, two years following initial clinicoradiologic presentation and twenty-two months following partial nephrectomy without additional therapy.

Conclusion

This report further expands the spectrum of morphologic and clinical findings previously described in melanotic Xp11 translocation renal cancer, a distinctive tumor showing overlapping features between Xp11 translocation renal cell carcinoma, melanoma, and perivascular epithelioid cell neoplasms.

Virtual slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/7225796341180634

The clinical and CT imaging features of metanephric adenoma

BACKGROUND

Patients with metanephric adenoma have a good prognosis after undergoing total nephrectomy or local resection with kidney preservation. Accurate diagnosing is important for guiding clinical treatment. Only few previous case reports have been found focusing on the imaging findings of metanephric adenoma.

PURPOSE

To evaluate the multislice computed tomography (MSCT) imaging characteristics of metanephric adenoma.

MATERIAL AND METHODS

The imaging findings in eight patients with metanephric adenoma were studied retrospectively. MSCT was undertaken to investigate tumor location, size, attenuation, cystic or solid appearance, calcification, capsule sign, and enhancement pattern.

RESULTS

Tumors (mean diameter, 3.3 ± 1.0 cm) were solitary (8/8), solid (7/8) with cystic components (2/8), no calcifications (7/8), had a poorly-defined margin (8/8), were centered in the renal medulla (7/8), compressed the renal pelvis (3/8), and none had retroperitoneal lymph node metastasis. The attenuation of metanephric adenoma tumors was less or equal compared to the renal cortex or medulla on unenhanced CT (30.6 ± 2.6 vs. 36.3 ± 4.6 vs. 33.2 ± 3.9, P > 0.05), while tumor enhancement after administration of an contrast agent was lower than that of normal renal cortex and medulla during all phases (P < 0.05).

CONCLUSION

Metanephric adenoma tends to be a solitary, poorly defined margin, isodense or hypodense mass arising from the renal medulla with enhancement less than the cortex and medulla during all phases.

Establishment of an ASPL-TFE3 renal cell carcinoma cell line (S-TFE)

Xp11 translocation renal cell carcinoma is a rare disease diagnosed in children and adolescents in the advanced stage with an aggressive clinical course. Various gene fusions including the transcription factor E3 (TFE3) gene located on chromosome X cause the tumor. We established an Xp11 translocation renal cell carcinoma cell line from a renal tumor in a 18-y-old Japanese female and named it "S-TFE." The cell line and its xenograft demonstrated definite gene fusion including TFE3. They showed strong nuclear staining for TFE3 in immunohistochemistry, TFE3 gene rearrangement in dual-color, break-apart FISH analysis and ASPL-TFE3 type 1 fusion transcripts detected by RT-PCR and direct DNA sequencing. Although many renal cell carcinoma cell lines have been established and investigated, only a few cell lines are recognized as Xp11.2 translocation carcinoma. S-TFE will be useful to examine the characteristics and drug susceptibility of Xp11 translocation renal cell carcinoma.

Paragangliomas: update on differential diagnostic considerations, composite tumors, and recent genetic developments

Recent developments in molecular genetics have expanded the spectrum of disorders associated with pheochromocytomas (PCCs) and extra-adrenal paragangliomas (PGLs) and have increased the roles of pathologists in helping to guide patient care. At least 30% of these tumors are now known to be hereditary, and germline mutations of at least 10 genes are known to cause the tumors to develop. Genotype-phenotype correlations have been identified, including differences in tumor distribution, catecholamine production, and risk of metastasis, and types of tumors not previously associated with PCC/PGL are now considered in the spectrum of hereditary disease. Important new findings are that mutations of succinate dehydrogenase genes SDHA, SDHB, SDHC, SDHD, and SDHAF2 (collectively "SDHx") are responsible for a large percentage of hereditary PCC/PGL and that SDHB mutations are strongly correlated with extra-adrenal tumor location, metastasis, and poor prognosis. Further, gastrointestinal stromal tumors and renal tumors are now associated with SDHx mutations. A PCC or PGL caused by any of the hereditary susceptibility genes can present as a solitary, apparently sporadic, tumor, and substantial numbers of patients presenting with apparently sporadic tumors harbor occult germline mutations of susceptibility genes. Current roles of pathologists are differential diagnosis of primary tumors and metastases, identification of clues to occult hereditary disease, and triaging of patients for optimal genetic testing by immunohistochemical staining of tumor tissue for the loss of SDHB and SDHA protein. Diagnostic pitfalls are posed by morphological variants of PCC/PGL, unusual anatomic sites of occurrence, and coexisting neuroendocrine tumors of other types in some hereditary syndromes. These pitfalls can be avoided by judicious use of appropriate immunohistochemical stains. Aside from loss of staining for SDHB, criteria for predicting risk of metastasis are still controversial, and "malignancy" is diagnosed only after metastases have occurred. All PCCs/PGLs are considered to pose some risk of metastasis, and long-term follow-up is advised.

TFE3 break-apart FISH has a higher sensitivity for Xp11.2 translocation-associated renal cell carcinoma compared with TFE3 or cathepsin K immunohistochemical staining alone: expanding the morphologic spectrum

Renal cell carcinoma (RCC) associated with Xp11.2 translocation is uncommon, characterized by several different translocations involving the TFE3 gene. We assessed the utility of break-apart fluorescence in situ hybridization (FISH) in establishing the diagnosis for suspected or unclassified cases with negative or equivocal TFE3 immunostaining by analyzing 24 renal cancers with break-apart TFE3 FISH and comparing the molecular findings with the results of TFE3 and cathepsin K immunostaining in the same tumors. Ten tumors were originally diagnosed as Xp11.2 RCC on the basis of positive TFE3 immunostaining, and 14 were originally considered unclassified RCCs with negative or equivocal TFE3 staining, but with a range of features suspicious for Xp11.2 RCC. Seventeen cases showed TFE3 rearrangement associated with Xp11.2 translocation by FISH, including all 13 tumors with moderate or strong TFE3 (n=10) or cathepsin K (n=7) immunoreactivity. FISH-positive cases showed negative or equivocal immunoreactivity for TFE3 or cathepsin K in 7 and 10 tumors, respectively (both=3). None had positive immunohistochemistry but negative FISH. Morphologic features were typical for Xp11.2 RCC in 10/17 tumors. Unusual features included 1 melanotic Xp11.2 renal cancer, 1 tumor with mixed features of Xp11.2 RCC and clear cell RCC, and other tumors mimicking clear cell RCC, multilocular cystic RCC, or high-grade urothelial carcinoma. Morphology mimicking high-grade urothelial carcinoma has not been previously reported in these tumors. Psammoma bodies, hyalinized stroma, and intracellular pigment were preferentially identified in FISH-positive cases compared with FISH-negative cases. Our results support the clinical application of a TFE3 break-apart FISH assay for diagnosis and confirmation of Xp11.2 RCC and further expand the histopathologic spectrum of these neoplasms to include tumors with unusual features. A renal tumor with pathologic or clinical features highly suggestive of translocation-associated RCC but exhibiting negative or equivocal TFE3 immunostaining should be evaluated by TFE3 FISH assay to fully assess this possibility.

The multislice CT findings of renal carcinoma associated with XP11.2 translocation/TFE gene fusion and collecting duct carcinoma

BACKGROUND

Renal cell carcinoma associated with Xp11.2 translocation and TFE gene fusion (Xp11.2/TFE RCC), and collecting duct carcinoma (CDC) are uncommon subtypes of renal cell carcinomas.

PURPOSE

To investigate the multislice CT (MSCT) characteristics of these two tumor types.

MATERIAL AND METHODS

Nine patients with Xp11.2/TFE RCC and 10 patients with CDC were studied retrospectively. MSCT was undertaken to investigate differences in tumor characteristics and enhancement patterns.

RESULTS

All patients had single tumors centered in the renal medulla. Two patients with each tumor type had lymph node involvement and there was a single case of hepatic metastasis (Xp11.2/TFE RCC). The mean tumor diameter of Xp11.2/TFE RCC tumors was significantly larger than for CDC tumors. Two patients with Xp11.2/TFE RCC had cystic components as did eight patients with CDC (P < 0.05). Calcifications were present in six patients, each with CDC. Clear tumor boundaries were visible in two patients with CDC and in nine with Xp11.2/TFE RCC (P < 0.05). The density of Xp11.2/TFE RCC tumors was greater than that of CDC tumors, normal renal cortex, or medulla on unenhanced CT. Enhancement was higher with Xp11.2/TFE RCC than with CDC tumors during all phases. Xp11.2/TFE RCC enhancement was higher than in the renal medulla during cortical and medullary phase but lower than in normal renal medulla during the delayed phase. CDC tumor enhancement was lower than that for normal renal medulla during all enhanced phases.

CONCLUSION

Both tumor types originated from the renal medulla. Distinguishing features included density on unenhanced CT, enhancement patterns, and capsule signs. Identifying these differences may aid diagnosis.

Transition of organizational category on renal cancer

The incidence of kidney cancer is gradually increasing, with a rate of 2-3% per decade. The kidney develops various kinds of neoplasms, some of which are associated with familial cancer syndromes. Such cases have provided clues to identify the cancer-responsible genes. In 2004, the World Health Organization published a new classification system of renal neoplasms, incorporating recent knowledge obtained in the cytogenetic and molecular biological fields, i.e. genes responsible for each histologic subtype (von Hippel-Lindau for clear cell renal cell carcinoma, c-met for papillary renal cell carcinoma type 1, etc.). Subsequently, the Japanese classification system in 'the General Rule for Clinicopathological Study of Renal Cell Carcinoma' has been revised as the 4th edition, according to the World Health Organization system. Several novel subtypes have been introduced, i.e. mucinous tubular and spindle cell carcinoma, and Xp11.2/TFE3 translocation-associated renal cell carcinoma. Even after the publication of the classification, other novel subtypes have emerged, i.e. acquired cystic disease-associated renal cell carcinoma and tubulocystic renal cell carcinoma. Additionally, some of the subtypes seem to form families based on morphological transition, immunohistochemical features and gene expression profile. In future, the classification of renal cell carcinoma should be reorganized on the basis of molecular biological characteristics to establish personalized therapeutic strategies.

Perivascular epithelioid cell neoplasm of the urinary bladder in an adolescent: a case report and review of the literature

Abstract

Perivascular epithelioid cell neoplasms (PEComas) of the urinary bladder are extremely rare and the published cases were comprised predominantly of middle-aged patients. Herein, the authors present the first urinary bladder PEComa occurring in an adolescent. This 16-year-old Chinese girl present with a 3-year history of abdominal discomfort and a solid mass was documented in the urinary bladder by ultrasonography. Two years later, at the age of 18, the patient underwent transurethral resection of the bladder tumor. Microscopically, the tumor was composed of spindled cells mixed with epithelioid cells. Immunohistochemically, the tumor were strongly positive for HMB45, smooth muscle actin, muscle-specific actin, and H-caldesmon. Fluorescence in situ hybridization analysis revealed no evidence of EWSR1 gene rearrangement. The patient had been in a good status without evidence of recurrence 13 months after surgery. Urinary bladder PEComa is an extremely rare neoplasm and seems occur predominantly in middle-aged patients. However, this peculiar lesion can develop in pediatric population and therefore it should be rigorously distinguished from their mimickers.

Virtual slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1870004378817301

A renal epithelioid angiomyolipoma/perivascular epithelioid cell tumor with TFE3 gene break visualized by FISH

We present a case of renal epithelioid angiomyolipoma (eAML)/perivascular epithelioid cell tumor (PEComa) with a TFE3 gene break visible by fluorescence in situ hybridization (FISH). Histologically, the tumor was composed of mainly epithelioid cells forming solid arrangements with small foci of spindle cells. In a small portion of the tumor, neoplastic cells displayed nuclear pleomorphism, such as polygonal and enlarged vesicular nuclei with prominent nucleoli. Marked vascularity was noticeable in the background, and perivascular hyaline sclerosis was also seen. Immunohistochemically, neoplastic cells were diffusely positive for α-smooth muscle actin and melanosome in the cytoplasm. Nuclei of many neoplastic cells were positive for TFE3. FISH analysis of the TFE3 gene break using the Poseidon TFE3 (Xp11) Break probe revealed positive results. Reverse transcriptase-polymerase chain reactions (RT-PCR) for ASPL/TFE3, PRCC/TFE3, CLTC/TFE3, PSF/TFE3, and NonO/TFE3 gene fusions all revealed negative results. This is the first reported case of renal eAML/PEComa with a TFE3 gene break, and it has unique histological findings as compared to previously reported TFE3 gene fusion-positive PEComas. Pathologists should recognize that PEComa with TFE3 gene fusion can arise even in the kidney.

WITHDRAWN: Comparative study of CT appearances in renal carcinoma associated with Xp11.2 translocation/TFE gene fusion and papillary renal cell carcinoma

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Melanotic xp11.2 neoplasm of the ovary: report of a unique case

We describe a primary ovarian neoplasm, occurring in a 15-year-old female patient, with morphologic, immunohistochemical, and molecular genetic features identical to those of the very rare tumors of the kidney previously described as "melanotic Xp11 translocation renal cancer." This represents, to the best of our knowledge, the first report of a melanotic Xp11 translocation-associated neoplasm arising outside of the kidney. We discuss the relationship of these rare tumors to neoplasms showing perivascular epithelioid cell differentiation, in particular those showing TFE3 rearrangements.

Translocation renal cell carcinomas in adults: a single-institution experience

Translocation renal cell carcinoma is a newly recognized subtype of renal cell carcinoma (RCC) with chromosomal translocations involving TFE3 (Xp11.2) or, less frequently, TFEB (6p21). Xp11 translocation RCC was originally described as a pediatric neoplasm representing 20% to 40% of pediatric RCCs, with a much lower frequency in the adult population. TFEB translocation RCC is very rare, with approximately 10 cases reported in the literature. Here, we describe the clinicopathologic features of adult translocation RCC from a single institution. Using tissue microarray, immunohistochemistry, cytogenetic examination, and fluorescence in situ hybridization, we identified 6 (∼5%) cases of TFE3 translocation RCC and 1 (<1%) case of TFEB translocation RCC in 121 consecutive adult RCC cases between 2001 and 2009. Our results suggest that weak TFE3 staining of a significant proportion of RCC cases may be because of expression of the full-length TFE3 protein rather than the chimeric fusion protein resulting from chromosomal translocation.

TFE3 rearrangements in adult renal cell carcinoma: clinical and pathologic features with outcome in a large series of consecutively treated patients

Renal cell carcinoma (RCC) with chromosomal rearrangement of transcription factor for immunoglobulin heavy-chain enhancer 3 (TFE3) at Xp11.2 is a distinct subtype that was initially described in children and has been reported to display an indolent course. Recent reports have identified RCC with TFE3 rearrangements in adults and have suggested a more aggressive course in this population. However, only a few studies have examined these tumors in a large series of consecutively treated adults. We screened 632 RCCs from patients consecutively treated by surgery at a single institution by fluorescence in situ hybridization to detect TFE3 rearrangements. We identified 6 RCCs with TFE3 rearrangement. Patient ages ranged from 25 to 78 years and included 4 women and 2 men. Tumors showed significant histologic variability. Comparison of the clinical and pathologic features between RCCs with TFE3 rearrangements and RCCs without TFE3 rearrangements showed no significant differences. Follow-up period for patients with TFE3-rearranged RCC ranged from 0.8 to 16.5 years, with 4 of 6 dying from the disease. Cancer-specific survival for patients with TFE3-rearranged RCC was significantly worse than for patients with TFE3-rearrangement-negative papillary-type RCC (P<0.001) but not different from that for TFE3-rearrangement-negative clear cell-type RCC. In conclusion, we present an assessment of TFE3 rearrangement status in a large series of adults consecutively treated by surgery for RCC. Our findings confirm that RCCs with TFE3 rearrangement account for only approximately 1% of adult RCCs. The results also suggest that adult RCC with TFE3 rearrangement may be a clinically aggressive tumor.

Current pathology keys of renal cell carcinoma

CONTEXT

Renal cell carcinoma (RCC) in adults comprises a heterogeneous group of tumours with variable clinical outcomes that range from indolent to overtly malignant. The application of molecular genetic techniques to the study of renal neoplasms has resulted in an improved classification of these entities and a better understanding of the biologic mechanisms responsible for tumour development and progression. The current 2004 World Health Organisation classification of adult renal epithelial neoplasms has expanded rapidly with new categories recently incorporated.

OBJECTIVE

To review and evaluate the evidence implicating pathologic features and classification of RCC in adults as a tool to approach patients' prognosis and modulate current therapy.

EVIDENCE ACQUISITION

Members of Committee 3: Pathology, under the auspices of the International Consultation on Urological Diseases and the European Association of Urology (ICUD-EAU) International Consultation on Kidney Cancer, performed a systematic review using PubMed. Participating pathologists discussed pathologic categories and diagnostic features of RCC in adults.

EVIDENCE SYNTHESIS

We reviewed and discussed articles and the personal experiences of participating uropathologists.

CONCLUSIONS

The conclusions reached by the ICUD-EAU 2010 International Consultation on Kidney Cancer emphasise the appropriate pathologic diagnosis of RCC in adults as a tool to approach patients' prognosis and modulate current therapy. Further emphasis should be placed on defining risk groups of RCC and diagnostic features of unusual tumours such as familial RCC, translocation RCC, and tubular mucinous and spindle cell carcinoma. A number of recently described entities and morphologic variants of classical categories deserves recognition because they can be important in differential diagnosis and therapy.

An Adult Case of Melanotic Xp11 Translocation Renal Cancers: Distinct Entity or Sub-entity?

Melanotic Xp11 translocation renal cancer is a recently recognized aggressive epithelioid neoplasm with features overlapping between PEComa, carcinoma, and melanoma, in which TFE3 gene fusions coexist with melanin synthesis. These findings support the idea that melanotic Xp11 translocation renal cancer is a distinct variant of the MiT/TFE3 family neoplasms. The authors describe a pigmented renal tumor occurring in a 30-year-old woman with distinct morphology and immunohistochemical characteristics as Xp11 translocation renal cancer.

Renal cell carcinoma in children and adolescents

Although rare in children and adolescents, renal cell carcinomas (RCCs) raise important questions concerning the best treatment approach and accurate pathologic classification. The differences emerging between childhood and adulthood RCC probably prevent any direct generalized application of therapies to children that are validated for adults. The translocation type of RCC, which forms a distinct category characterized by translocations involving Xp11.2 or, less frequently, 6p21, has recently emerged as the predominant type of RCC in children and adolescents, whereas it is rarely diagnosed in adults. This new finding emphasizes how important it is to prospectively classify RCCs in children with standardized 'modern' diagnoses. The standard cornerstone of therapy for RCC in children and adolescents remains radical nephrectomy. Nephron-sparing surgery is currently recommended in adults for selected small-volume tumors, but additional data are needed before this experience can be extensively transferred to the pediatric population. The therapeutic value of complete retroperitoneal lymph node dissection is still controversial, especially in patients without suspected nodal involvement, be they adults or children. The backbone of systemic therapies for adult RCC has recently been changed by the introduction of drugs designed to target tumor-related angiogenesis and signal transduction. It is worth noting that the largest clinical efficacy trials on targeted molecules have been conducted on clear-cell RCC. While targeted drugs have become the standard of care for adult metastatic RCC, there are currently no published reports on their role in children, and their use should be considered for patients with unresectable metastatic or advanced-stage RCC. On the other hand, the utility of targeted therapies in the adjuvant setting remains to be seen for both adults and children.

A distinctive subset of PEComas harbors TFE3 gene fusions

Perivascular epithelioid cell neoplasms (PEComas) include the common renal angiomyolipoma, pulmonary clear cell sugar tumor, lymphangioleiomyomatosis, and less common neoplasms of soft tissue, gynecologic, and gastrointestinal tracts. Recently, aberrant immunoreactivity for TFE3 protein (a sensitive and specific marker of neoplasms harboring TFE3 gene fusions) has been reported in as many as 100% of PEComas; however, TFE3 gene status in these neoplasms has not been systematically investigated. We used a fluorescence in situ hybridization (FISH) break-apart assay to evaluate for evidence of TFE3 gene fusions in archival material from 29 PEComas. These cases included 2 earlier published TFE3 immunoreactive nonrenal PEComas, 14 additional nonrenal PEComas, and 13 renal angiomyolipomas with predominantly spindle or epithelioid morphology. Four nonrenal PEComas (mean patient age 24 y) showed TFE3 gene rearrangements by FISH, and all 4 of these showed strong positive (3+) TFE3 immunoreactivity using the original validated overnight incubation protocol. Two of these cases had adequate mRNA for RT-PCR analysis, but neither harbored the PSF-TFE3 gene fusion reported earlier in 1 PEComa. In addition, a lung metastasis of a uterine PEComa showed TFE3 gene amplification, an earlier unreported phenomenon. None of the other 24 PEComas (mean patient age 54 y) showed TFE3 gene alterations, though 4 exhibited moderate positive (2+) TFE3 immunoreactivity. In contrast, using an automated stainer, 2 of these 4 cases exhibited strong (3+) TFE3 immunoreactivity. All PEComas with TFE3 genetic alterations immunolabeled strongly for Cathepsin K, similar to other PEComas. In conclusion, a subset of lesions currently classified as PEComas harbors TFE3 gene fusions. Although numbers are small, distinctive features of these cases include a tendency to young age, the absence of association with tuberous sclerosis, predominant alveolar architecture and epithelioid cytology, minimal immunoreactivity for muscle markers, and strong (3+) TFE3 immunoreactivity. Despite significant morphologic and immunohistochemical overlap with other PEComas, PEComas harboring TFE3 gene fusions may represent a distinctive entity.

The pediatric renal clear cell "sugar" tumor: pseudo-alveolar structure mimicking clear cell renal carcinoma

The primary extrapulmonary sugar tumor (PEST) is rare. Up to now, only 16 cases of PEST have been reported, including 5 pediatric cases. We report a renal benign PEST in a 16-year-old boy, which is the first such case to be reported in the pediatric kidney. The tumor was composed of clear and eosinophilic epithelioid cells, growing with nest and pseudoalveolar structure, which can be confused with renal clear cell carcinoma. The tumor cells were positive for melanocytic and negative for epithelial markers. The tumor was enucleated, and the patient was well without recurrence 21 months after surgery.