Chordoma with a massive spindle-cell sarcomatous transformation. A light- and electron-microscopic and immunohistological study.

A 26-year-old woman was operated on for a bulky tumor in the sacral region; she died of massive local tumor recurrence and pulmonary metastases 3 months later. Most of the original tumor showed a highly cellular spindle-cell sarcoma compatible with a fibrosarcoma of a high grade of malignancy. In a few small areas of the tumor, a chordoma-like pattern surrounded by growth of spindle-cell sarcoma was found. The spindle-cell component exhibited vimentin positivity in all tumor cells, but many cells were also cytokeratin-positive. The chordoma-like areas showed cytokeratin in all tumor cells. The chordoma-like areas, but not the spindle-cell areas also were positive for epithelial membrane antigen and S-100 protein. This case indicates that the sarcomatous change associated with chordoma may contain keratins as a sign of epithelial differentiation, and may thus represent sarcomatous transformation of chordoma cells, rather than a coincidental soft-tissue sarcoma or collision tumor.