Extraskeletal myxoid chondrosarcoma with "chordoid" features (chordoid sarcoma).

The light and electron microscopic features of a so-called chordoid sarcoma arising in the area of the gastrocolic ligament are described and illustrated. Despite the tumor's histologic resemblance to chordoma, the ultrastructural markers are those of chondroid rather than chordoid neoplasms. These are well-developed, vesciular granular endoplasmic reticulum, intracytoplasmic glycogen, lipid bodies, and a collagen-poor extracellular matrix with electron-dense granules, presumably representing chondroitin sulfate. Similar submicroscopic alterations have been observed in extraskeletal myxoid chondrosarcomas. Because of the distinctive morphologic appearance of this peculiar lesion, the term "myxoid chondrosarcoma with chordoid features" is suggested to reconcile histologic and ultrastructural features and histogenesis.