Invasive squamous cell carcinoma within a plaque of circumscribed palmar hypokeratosis.

Circumscribed palmar hypokeratosis (CPH) is a localized disorder of epidermal keratinization that is presented as a well-delimited, depressed, erythematous plaque on the palms or on the soles. It is histopathologically characterized by an abrupt thinning of the corneal epidermal layer. CPH is considered a benign condition, but a few cases with dysplastic changes/carcinoma in situ in the hypokeratotic epidermis have been described. We report hereby a case of invasive squamous cell carcinoma developed within a plaque of CPH. The pathogenesis of the malignant changes in this disorder remains to be clarified. Clinicians should be aware of the potential for developing malignancy in CPH and carry out a closer follow-up of this disorder.