Anti-pan Cytokeratin monoclonal antibody, clone E-23 [PE]

Synovial sarcoma (SS) is a morphologically characteristic sarcoma of uncertain lineage, typically containing both epithelial and mesenchymal elements. The most common location is the extremities, and very few cases have been reported from the head and neck region. The monophasic spindle cell variant often poses a diagnostic challenge as it mimics poorly differentiated carcinoma or sarcoma. We report a case of monophasic SS of tongue in a 74-year-old female. On Immunohistochemistry, the tumor cells showed strong, diffuse positivity for vimentin, Bcl-2, CD99, and focal positivity for epithelial membrane antigen. Tumor cells were negative for pan cytokeratin, smooth muscle actin, S100, HMB-45, CD34. A high index of clinical suscipicion is required to reach an accurate diagnosis for institution of appropriate therapy.

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.