Melanoma within the seborrheic keratosis.

Seborrheic keratoses (SKs) are common benign nonmelanocytic epidermal tumors with characteristic clinical features, which are thought to allow a straightforward diagnosis in most situations. As a result, it is an accepted practice to destroy them without histopathologic confirmation. However, systematic reviews of histologic specimens reveal an erroneous clinical diagnosis or associated malignant tumors in a number of cases, including malignant melanomas. We describe a patient with a clinically typical-appearing SK, which was biopsied and histologically proven to be a malignant melanoma arising in the SK. Our report is a reminder that the reliability of clinical diagnosis of SKs needs to be questioned. In addition, a biopsy of SKs is not only warranted but necessary in order to identify a malignant melanoma that would otherwise be misdiagnosed or even completely missed.