Occult basal cell carcinoma arising in seborrheic keratosis

The present study reports a case of an occult basal cell carcinoma that arose in seborrheic keratosis. The patient was a fifty-six-year-old male who presented with a dark brown plaque on his back. Clinically, the lesion demonstrated no nodules or ulcerations suggesting that it was malignant. However, histopathological analysis of the lesion revealed an atypical basaloid cell mass that appeared to be a solid basal cell carcinoma beneath and surrounded by a seborrheic keratosis lesion. Thus, the coexistence of basal cell carcinoma and seborrheic keratosis is possible and should be considered when a malignant change in seborrheic keratosis is apparent.