Prevalence of melanoma clinically resembling seborrheic keratosis - Analysis of 9204 cases

Objective: To estimate the prevalence of melanoma clinically mimicking seborrheic keratosis. Design: Retrospective review of cases submitted for histological examination with a clinical diagnosis of seborrheic keratosis or with a differential diagnosis that included seborrheic keratosis. Setting: A tertiary medical care center-based dermatopathology laboratory serving academic dermatology clinics that have a busy pigmented lesion clinic. Materials and Methods: A total of 9204 consecutive pathology reports containing a diagnosis of seborrheic keratosis; in the clinical information field were identified between the years 1992 and 2001 through a computer database search. Reports with a final histological diagnosis of melanoma were selected for further review and clinicopathological analysis. Main Outcome Measure: Histological diagnosis, which was correlated with the preoperative clinical diagnosis. Results: Melanoma was identified in 61 cases (0.66%) submitted for histological examination with a clinical diagnosis that included seborrheic keratosis. Melanoma was in the clinical differential diagnosis of 31 cases (51%). The remaining lesions had a differential diagnosis of seborrheic keratosis vs melanocytic nevus (17 cases, 28%), basal cell carcinoma (7 cases, 12%), or a squamous proliferation (3 cases, 5%). In 3 cases (5%), seborrheic keratosis was the only clinical diagnosis. All histological types of melanoma were represented. Conclusions: Our results confirm that melanoma can mimic seborrheic keratosis. These data strongly support the current policy of submitting for histological examination all specimens that have been removed from patients.