Ultrastructure of the so-called "chordoid sarcoma". Evidence supporting cartilagenous differentiation.

A rare, distinctive neoplasm occurring in the soft tissue of the extremities and resembling chordoma has been recently described and variously termed "chordoid sarcoma," "chordoid tumor," and "parachordoma." An example of this tumor occurring in the flank is presented. The tumor lacks the ultrastructural features associated with chordomas. Moreover, the tumor appears to be elaborating an abundant matrix of sulfated acid mucopolysaccharide interspersed with collagen fibers in varying stages of maturation. These features suggest that the tumor is exhibiting chondroid, rather than chordoid, differentiation. Previous reports of extraskeletal myxoid chondrosarcoma bear a striking light microscopic and electron microscopic similarity to the "chordoid sarcoma," suggesting that the latter is a variant of extraskeletal myxoid chondrosarcoma.