Are All Seborrheic Keratoses Benign? Review of the Typical Lesion and Its Variants

BACKGROUND: Seborrheic keratosis (SK) is one of the more common benign epidermal neoplasms seen in adult and middle-aged patients. OBJECTIVE: As little is written in the literature about the variants of SK, this article aims to categorize and discuss the different subtypes and their important associations. METHODS: An in-depth literature search using OVID Medline and PubMed was conducted to classify the various subtypes of SK. Clinical variants were photographed and used to help document the subtypes. The pathology is described for each. RESULTS: Six subtypes of SK were identified: dermatosis papulosa nigra, stucco keratosis, inverted follicular keratosis, large cell acanthoma, lichenoid keratosis, and flat seborrheic keratosis. Although the etiology and pathogenesis of SKs are still largely debatable, several underlying mechanisms and contributing factors have been identified. All subtypes represent benign lesions, and treatment is usually done for cosmetic reasons. Several of the subtypes may act as cutaneous markers for internal malignancy and should be monitored closely for any atypical changes. CONCLUSION: Although all subtypes of SK are benign, their association with other malignant lesions and ability to serve as cutaneous markers of internal malignancy emphasize the importance of correctly identifying all variants.