Skin Moles

Typical acquired skin moles have not been followed systematically from their progression to regression. Therefore, dynamic evolution of acquired skin moles must be suggested from static information or short-term follow-up studies. It has been stated that during the early years of life, virtually all skin moles are composed primarily of junctional moles, that nevomelanocytes in these junctional moles eventually push their way to the dermis and finally lose their epidermal contact as they continue to grow into the dermis and become intradermal skin moles, and that in the intermediate stage of this process there are junctional moles in the epidermis and sheets and nests of nevomelanocytes in the dermis (i.e., compound skin moles). This argument suggests that because skin moles in adults are primarily of the dermal type and because skin moles in children are primarily of the junctional type, skin moles evolve by a process of “dropping down” of nevus cells from the epidermis into the dermis. The precise nature of the “dropping down” process has not been defined. It is likely that acquired skin moles evolve through a life cycle, first becoming apparent after infancy in the vast majority of cases, peaking in number during the second and third decades of life, and then disappearing by the seventh to ninth decades. Regression of skin moles is believed to occur by degeneration. The formation of degenerative structures in aging skin moles suggests an end stage in differentiation and not a source of origin of intraepidermal skin moles. Transepidermal elimination of nevomelanocytes rarely occurs. Rarely, nevomelanocytes have been documented to show spontaneous disappearance. Skin moles also may involute during the course of inflammatory halo depigmentation (halo moles). There may be relatively sudden changes in skin moles that are unrelated to cancerous transformation. Any single mole that is noted to suddenly change independently should be a cause for concern. Causes of sudden changes in a mole (color, surface, or size, with or without pain, itching, ulceration, or bleeding) over days or weeks include cystic dilatation of a hair follicle, epidermal cyst formation, folliculitis, abscess formation, trauma, hemorrhage, and, in the case of a pedunculated mole, strangulation and thrombosis. These benign causes of sudden change may require close observation until resolution occurs over the course of 7 to 10 days (in the case of trauma or inflammation) or histopathologic examination. Cases have been described of the eruptive appearance of skin moles after blistering skin disease, immunosuppression, or chemotherapy. The vast majority of acquired skin moles are harmless, growing in proportion to body growth, with physiologic spurts of enlargement during early childhood and puberty.
A cancerous mole risk appears to be related to the number and size of skin moles; patients with numerous skin moles, atypical skin moles, and a personal or family history of a cancerous mole should be considered for periodic surveillance examinations.