Clinical Misdiagnosis of Squamous Cell Carcinoma In Situ as Seborrheic Keratosis A Prospective Study

BACKGROUND: Seborrheic keratoses have on rare occasion been reported to undergo malignant transformation. OBJECTIVE: Our purpose was to examine the incidence and distribution of squamous cell carcinomas (SCCs) in situ arising in clinically banal-appearing seborrheic keratoses. METHODS: We prospectively selected such cases over a 6-month period of time from routinely accessioned specimens to a dermatopathology service. RESULTS: We found 1.4% of clinically diagnosed seborrheic keratoses to be SCCs in situ. These lesions were more common in elderly persons and were more likely to occur on the head and neck, suggesting the role of cumulative sun damage in the transformation of such lesions. CONCLUSION: Malignant transformation of seborrheic keratoses, although rare, appears to occur more frequently in the elderly on the head and neck. Because this change is not necessarily accompanied by clinically discernable changes, more careful scrutiny of such lesions may be of therapeutic rather than cosmetic significance in this population.