[Retroperitoneal extraskeletal myxoid chondrosarcoma].
Extraskeletal myxoid chondrosarcoma is a rare soft tissue tumor included by WHO in the group of tumors of uncertain differentiation because well formed cartilage is rarely seen in its setting; moreover some of the immunophenotype features of the tumor are still controversial. The reciprocal translocation t(9;22)(q22;q12) has recently been identified in many cases, and this chromosomal aberration is currently considered high specific of this tumor. We report the case of a 75-year-old female submitted to radical nephrectomy for a voluminous kidney tumor with radiological evidence of extrarenal extension. Grossly the lesion was set in the perirenal fat tissue. Histological examination revealed a malignant mesenchimal tumor with myxoid f eatures and areas of chondroid differentiation consistent with the diagnosis of extraskeletal myxoid chondrosarcoma. According with the diagnosis the tumor showed focal positivity to NSE by immunohistochemistry. Differentiated cartilage is seen in extraskeletal myxoid chondrosarcoma in about 30% of the cases. Our case is then interesting not only for the rare site of tumor location but also for the extension of chondroid differentiation areas found on histologic examination in the tumor setting. Moreover immunohistochemistry showed focal positivity of the neoplastic cells for NSE, according with recent studies demonstrating expression of some neural/neuroendocrine markers in extrascheletal myxoid chondrosarcoma.