Abstract

Dedifferentiated chordoma is a rare pathologic entity presenting an additional sarcomatous component in otherwise classical chordoma. It has been also emphasized that this neoplasm is classified as a distinct entity because of its different clinical settings and aggressive behavior. Dedifferentiation is a peculiar phenomenon but its histogenesis has remained controversial. A 50-yera-old man developed a huge tumor mass in the retrorectal, presacral area, featured with two histological components. The one was a typical chordoma accounted for approximately 60% of the mass and the other was made up of highly cellular, plemorphic, undifferentiated tumor cells, reminiscent partly to the cells of plemorphic malignant fibrous histiocytoma. Ultrastructural features and immunoreactivity against cytokeratin, S-100 protein and alpha-1-antichymotrypsin in both portions support that histologically different components of this neoplasm derive from the same origin. To our knowledge, this is the first case of dedifferentiated chordoma in Korea.

• Keywords: Dedifferentiation;Chordoma;Dedifferentiated chordoma