Case-of-the-Month - February 1997

Pathology

Electron microscopy

Electron microscopy showed (Fig 5) that the tumor cells were polygonal with central, rounded nuclei, inconspicuous nucleoli and relatively abundant cytoplasm. A number of cells had short, slightly tapering cytoplasmic extensions or processes, overlapping with those of adjacent cells but without marked interdigitation. Many cells had abundant cytoplasm with perinuclear, tangled whorls of intermediate filaments, which extended into cell processes (Fig 6). They were mainly vimentin but immunoelectron microscopy also confirmed the presence of desmin in some cells. A second distinctive feature was the presence on cell bodies of short fragments of thick external lamina (Fig 7). Rough endoplasmic reticulum was not prominent and the microtubular aggregates, characteristic of extraskeletal myxoid chondrosarcoma, were lacking.

Figure 5. Electron microscopy shows rounded nuclei with inconspicuous nucleoli and cytoplasm extending into overlapping, vaguely interdigitating processes.	Figure 6. The cytoplasm contains intermediate filaments, in a perinuclear distribution, and extending into the cell processes.
Figure 7. A distinct, thick external lamina (arrows) covers parts of the cell body.

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