Epidermal apoptosis: cell deletion by phagocytosis.

Apoptosis is a process found in many tissues by which devitalized cells are eliminated in an orderly manner. In skin, apoptosis occurs following sunburn, in Bowen's disease and in basal cell carcinoma. Scattered cells are observed in which the cytoplasm has become condensed and dyskeratotic. These dyskeratotic cells are phagocytized, either in toto or in fragments by surrounding keratinocytes. This process involves the condensation, fragmentation, phagocytosis and digestion of individually degenerated cells. The mass of a tissue is thus related to the balance between cell formation (mitosis) and cell destruction (apoptosis). In epidermal and other surface tissues, the rate of exfoliation must also be considered.