Acantholytic variant of seborrheic keratosis.

From among 524 histologic specimens of seborrheic keratosis (SK), 29 showed acantholysis, not related to pemphigus, Darier's disease, actinic keratosis or acantholytic squamous cell carcinoma. Acantholysis was found in 24 (23.3%) of the irritated type of SK, almost exclusively in the squamous cell nests showing dyskeratosis and spongiosis between and around squamous eddies or horn cysts. Clinically, 65.5% of the lesions were located on the face and scalp, 20.7% on the trunk and 13.8% on the limbs. It was speculated that dyskeratotic, degenerative changes of the keratinocytes together with spongiosis were responsible for the acantholysis.