We describe a case of extraskeletal myxoid chondrosarcoma with neuroendocrine differentiation. The tumor occurred in subcutaneous tissue of the right popliteal region in a 50-year-old man. It measured 5 cm in diameter, was well circumscribed, lobular and gelatinous, and lacked any necrosis or hemorrhage. Histologically, the tumor structure was a typical of extraskeletal myxoid chondrosarcoma. The lesion was lobulated and contained small to medium-sized chondroblast- like cells with ovoid hyperchromatic nuclei and without prominent nucleoli. The cells created cords and nests and showed focally a perivascular rosette-like arrangement. A few of the tumor cells were spindle shaped. The myxoid matrix was stained with alcian blue and this reaction was resistant to prior treatment with hyaluronidase. PAS-positive glycogen was found in the cyto- plasm of some tumor cells. Immunohistochemically, the tumor cells were diffusely positive for neuron specific enolase, monoclonal synaptophysin and vimentin. Following antibodies gave ne- gative results: desmin, actins, S-100 protein, pancytokeratin, epithelial membrane antigen, chro- mogranin A, neurofilament protein, myelinic basic protein, glial fibrillary acidic protein. The patient is well four years after the wide excision of tumor and radiotherapy. Neuroendocrine differentiation in extraskeletal myxoid chondrosarcoma was described at first by Chhieng et al. in 1998 ( 1 ). Our observation confirms this interesting finding.

        Key words: neuroendocrine differentiation - extraskeletal myxoid chondrosarcoma