mart-1-antigen and Keratosis--Seborrheic

We observed seborrheic keratoses with many basilar clear cells, creating a microscopic pattern that mimicked a seborrheic keratosis involved by melanoma in situ.. We sought to report a series of these seborrheic keratoses and the immunohistochemical stains used to reach a proper diagnosis.. We reviewed 9 cases of seborrheic keratosis that had a distinctive pattern of basal clear cells with ample cytoplasm. All cases were evaluated by conventional microscopy, and Melan-A, S-100, and high molecular weight keratin 903 immunostains.. The basal clear cells failed to react with Melan-A and S-100 protein antisera. In contrast, these cells labeled with an antikeratin antibody in all cases. In all, 7/9 (78%) showed immunopositivity only at the peripheries of cells, creating a pattern that could be mistaken for a negative stain if not examined at high magnification.. This is a retrospective review of cases limited to a large referral dermatopathology service.. We describe a previously uncharacterized pattern of seborrheic keratosis that can microscopically mimic melanoma in situ. Careful conventional microscopy coupled with a panel of immunostains can allow the proper diagnosis to be reached.

Topics: Aged; Aged, 80 and over; Antibodies; Antigens, Neoplasm; Diagnosis, Differential; Female; Humans; Immune Sera; Immunoenzyme Techniques; Keratins; Keratosis, Seborrheic; Male; MART-1 Antigen; Melanoma; Middle Aged; Neoplasm Proteins; Retrospective Studies; S100 Proteins; Skin Neoplasms; Staining and Labeling