Squamous cell carcinoma in situ (Bowen's disease) arising in seborrheic keratosis: three lesions in two patients.

Three lesions showing squamous cell carcinoma in situ (Bowen's disease) within seborrheic keratosis are reported: 2 were located symmetrically on the legs of one of the patients, with a lesion recurring after surgery. Nests of atypical cells were seen in the transitional zone between the 2 components of the third lesion.