[Extraskeletal myxoid chondrosarcoma of the nasopharynx].

Extraskeletal myxoid chondrosarcoma is a rare but distinct entity with special clinicopathological, immunohistochemical, cytogenetical and outcome features. This tumor developed from soft tissues. A few cases have been reported in the head and neck in the literature. We report two new cases of extraskeletal myxoid chrondrosarcoma presenting in such an unusual site: one involved the left nasal cavity of a 67-year-old man and the second the sphenoidal sinus of a 71-year-old woman. The microscopic examination revealed nests of round small cells dispersed in a myxoid stroma. The myxoid material was stained with Alcian Blue with and without hyaluronidase application whereas no PAS staining was observed. The immunohistochemical staining showed reactivity with S-100 protein and vimentin in two cases and with EMA in one case. These results allowed us to exclude other differential diagnoses: soft tissue tumors with a myxoid stroma (myxoma, myxoid liposarcoma and myxofibrosarcoma). No staining with anti-KL1 allowed us to exclude chordoma. Curative surgery was not possible. Both patients were given radiotherapy and the tumor regressed in one.