Atypical cells on reflectance confocal microscopy may not represent melanoma: A case of axillary pigmented extramammary Paget disease.

Pigmented extramammary Paget disease (PEMPD) is a rare intraepithelial carcinoma which can clinically resemble other pigmented neoplasms. Similarities to melanoma on dermoscopy, histopathology, and reflectance confocal microscopy (RCM) increase the risk of misdiagnosis and, consequently, mismanagement. Here, we describe a case of a 67-year-old African American woman with a large, pigmented axillary patch that exhibited features of melanoma on RCM, guiding the clinician to perform an excisional biopsy. While traditional histopathology resembled melanoma, immunohistochemistry staining was performed and revealed PEMPD. We highlight an uncommon clinical presentation of PEMPD disease and identify morphologic mimickers of melanoma on RCM-as well as differentiating features.