Basal cell epithelioma with giant tumor cells: light and electron microscopic study.

A case of basal cell epithelioma (BCE) with multiple large nuclei on the right buttock of a 69-year-old woman is reported, and the skin was studied by light and electron microscopy. This represented the only case (0.85%) of giant tumor cells with multiple nuclei among 117 patients with BCE. Ultrastructural studies revealed that giant tumor cells were not different from ordinary tumor cells of BCE, except for large convoluted nuclei. In the cytoplasms of giant tumor cells, we observed autophagic vacuoles which were derived from autophagocytosis. Scattered among the giant tumor cells, there were many degenerate tumor cells, some of which were phagocytized by giant tumor cells with multiple nuclei (referred to as macrophagocytosis). It is indicated that tumor cells have considerable phagocytic activities, and degrade the autophagic vacuoles or the degenerate tumor cells with the lysosomes. These findings suggest that the presence of the giant tumor cells with multiple nuclei does not indicate a increased malignant potential or anaplasia of the tumor, and that autophagocytosis or macrophagocytosis is a factor in initiating giant tumor cell formation.