Adamantinoid basal cell carcinoma. An ultrastructural study

We describe an adamantinoid basal cell carcinoma that has developed in the mucocutaneous border of the upper lip. An ultrastructural study disclosed three types of cells that were morphologically distinct in the tumor nest. Cells of the first type were basically the same as those of ordinary basal cell carcinoma. Cells of the second type showed varying degrees of cytoplasmic content loss in a worm-eaten pattern and seemed to consist of degenerating cells. Cells of the third type possessed a well-developed rough endoplasmic reticulum filled with medium electron-dense fine substance, which was also seen in the extracellular space. In relationship with the histochemical findings, and based on the histogenesis of adamantinoid basal cell carcinoma, we propose that subpopulations of tumor cells undergo spontaneous degeneration and that the spaces of such disappearing cells are refilled with products containing glycosaminoglycans secreted by another subpopulation of the tumor cells.