Background: We observed seborrheic keratoses with many basilar clear cells, creating a microscopic pattern that mimicked a seborrheic keratosis involved by melanoma in situ. Objective: We sought to report a series of ...Background: We observed seborrheic keratoses with many basilar clear cells, creating a microscopic pattern that mimicked a seborrheic keratosis involved by melanoma in situ. Objective: We sought to report a series of these seborrheic keratoses and the immunohistochemical stains used to reach a proper diagnosis. Methods: 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. Results: 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. Limitations: This is a retrospective review of cases limited to a large referral dermatopathology service. Conclusions: 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.展开更多
文摘Background: We observed seborrheic keratoses with many basilar clear cells, creating a microscopic pattern that mimicked a seborrheic keratosis involved by melanoma in situ. Objective: We sought to report a series of these seborrheic keratoses and the immunohistochemical stains used to reach a proper diagnosis. Methods: 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. Results: 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. Limitations: This is a retrospective review of cases limited to a large referral dermatopathology service. Conclusions: 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.
