Unilateral epidermal naevus resembling acanthosis nigricans.

A man born with a unilateral epidermal naevus on the right side of the abdomen developed at puberty symmetrical benign acanthosis nigricans in the body folds. The symmetrical eruption later disappeared completely. The unilateral epidermal naevus and the symmetrical eruption showed identical histological features, i.e. those of acanthosis nigricans. At the age of 32 he developed a muco-epidermoid cancer of the left parotid gland. A decision whether the association of unilateral epidermal naevi with malignant tumours occurs with unusual frequency requires (a) a long follow-up of the patient with the unilateral naevus, (b) a differentiation of the unilateral eruption from unilateral malignant acanthosis nigricans and (c) statistical evidence.