Dedifferentiated chordoma: a case report

Dedifferentiated chordoma, i.e. chordoma with a sarcomatous component, is a rare bone tumor. This case report is of a dedifferentiated chordoma in the sacrococcygeal region in a 50-year-old male. The patient was initially dia gnosed as having a leiomyosarcoma at the first medical consultation but aft er the tumor recurred it was proven to be a dedifferentiated chordoma. The primary tumor, which measured 7 x 5 cm, was located in front of the sacrum so as to compress the rectum forward. The resected specimen showed histolog ical features of chordoma, but the presence in some parts of the tumor of s pindle-shaped epithelial cells led to a misdiagnosis of leiomyosarcoma. Thi rty-six months later, a local recurrent tumor measuring 24 x 17 cm was iden tified and promptly resected. The recurrent tumor showed features of pleomo rphic cell sarcoma mimicking malignant fibrous histiocytoma. In the pleomor phic sarcomatous area, many mitotic figures were seen, and the MIB-1 labeli ng index was greater than 40%, which was higher than that of the convention al chordoma area. From histological and immunohistochemical examination, th e resected tumor was proven to be a dedifferentiated chordoma. This case hi ghlights the importance of careful study of suspected chordoma to allow ear ly identification of sarcomatous components. When we encounter a chordoma w ith a spindled epithelial component, we need to distinguish this tumor from a dedifferentiated chordoma and other spindle cell sarcomas such as leiomy osarcoma.