Two cases of basal cell carcinoma arising in seborrheic keratosis.

The present study reports two cases of basal cell carcinoma arising in seborrheic keratosis. The first case is a seventy-three-year-old female who presented with a blackish nodule arising from a pigmented lesion on her chest. Histopathological analysis of the nodule and the pigmented lesion revealed a basal cell carcinoma with hair follicular differentiation and an acanthotic seborrheic keratosis, respectively. The second case is a seventy-year-old female with a blackish nodule arising from a pigmented lesion on her back. Histological analysis of the nodule revealed an atypical basaloid cell mass surrounded by a seborrheic keratosis lesion. In addition to the coexisting seborrheic keratosis with the basal cell carcinoma, a basaloid follicular hamartoma that showed multiple hamartomatous hair follicles or small cysts replaced by a branching cord or lace-like network of basaloid cells surrounded by fibrovascular stroma was identified. We concluded that both cases presented a rare combination of a seborrheic keratosis which underwent a malignant change to basal cell carcinoma. It appears that both basal cell carcinomas and seborrheic keratosis may derive from a similar source: pluripotential cells of either the epidermis or hair follicle epithelium.