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