(3) The pathology and pathogenesis of stucco keratoses

Abstract

Stucco keratoses are benign acquired acral keratotic papular lesions usually occurring on the distal parts of the lower limbs of elderly men. They are poorly characterized in the literature and their pathogenesis is uncertain. We have studied eight patients with multiple stucco keratoses who presented in the previous 18 months, in an attempt to understand the nature of these lesions. All eight subjects were male, aged from 50 to 72 years. Their lesions had a characteristic stuck-on appearance and were most numerous over the fronts of the lower legs, but were also evident over other areas of the limbs. All patients had a history of prolonged solar exposure. Three of the subjects had concurrent facial solar keratoses (one also had a squamous cell carcinoma) and one had a lentigo maligna affecting the face. However, the stucco keratoses themselves showed no dysplastic change. Histologically, they showed a characteristic ‘church spire’ type retention hyperkeratosis without marked acanthosis. The lack of an obvious marked increase in epidermal cell population size is reflected in the normal in vitro tritiated thymidine autoradiographic labelling indices (7·81 ± 1·67%, normal range 5–9%). Ultrastructurally, there were no viral particles evident (confirmed by immunocytochemical studies) and a normal pattern of differentiation was evident. Two of the patients with myriads of lesions were treated for 2 months with etretinate and showed a dramatic improvement which, however, lasted for 6 months only. In summary, it appears that (i) these lesions are more common than previously believed; (ii) they are in some way the result of solar exposure, although not themselves dysplastic; (iii) they show normal epidermal differentiation, although they have a localized retention hyperkeratosis; and (iv) they respond to etretinate treatment.