Large-cell acanthoma. A distinctive keratosis.

Large-cell acanthoma is an epidermal neoplasm that is clinically, histologically, and biologically distinctive. Clinically, it differs from solar lentigo by being frequently skin-colored or hypopigmented. Histologically, it is defined by a population of uniformly large keratinocytes; it differs from solar lentigo by the absence of elongated hyperpigmented and sometimes hockey stick-shaped buds of keratinocytes. Biologically, it consists of hyperploid keratinocytes, whereas solar lentigo consists of diploid keratinocytes. Although the exact nosologic status of this entity is still controversial, its features are distinctive enough for the term "large-cell acanthoma" to merit continued usage.