Atypical fibroxanthoma of skin: an electron microscope study.

The ultrastructure of two atypical fibroxanthomas of skin is described. Most of the tumour cells were elongate, and contained abundant rough endoplasmic reticulum, well developed Golgi zones, and numerous small vesicles and filaments, the latter sometimes being related to masses of electron-dense material near the plasma-lemma. Their nuclei often showed deep surface indentations. The appearances were similar to those found in the socalled myfibroblasts that occur in granulation tissue. Multinucleated giant cells and lipid-laden cells in the tumours appeared to be merely modified forms of the basic cells type.