Palmar filiform hyperkeratosis: a new paraneoplastic syndrome?

Filiform hyperkeratosis of the palms and soles is a rare disorder. We describe a 70-year-old man with a 2-year history of multiple, filiform, keratotic projections on the palms and a nodular malignant melanoma on the back. Histopathologic examination of the palmar lesions revealed that each single keratotic projection was composed of a well-defined, compact parakeratotic column. The underlying epidermis showed a thinned granular layer. Five other cases of palmoplantar filiform hyperkeratosis in association with malignant neoplasms have been reported. Filiform hyperkeratosis of the palms and soles may represent a distinct paraneoplastic condition.