Irregular Pigmented Lesion on the Oral Mucosa

Abstract

A woman in her 50s presented with a several-week history of asymptomaticdark lesionsonher lowermucosal lip.Thepatientwas not taking anymedications at the time the lesiondeveloped. Physical examination revealed brown to black coalescing irregular macules involving a largeportionof her lower labialmucosa (Figure, A). Nopigmented lesionswere seenonother areas of theoralmucosa, on the ocular mucosa, or on the skin or nails. An incisional punch biopsy specimen from a pigmented macule was submitted for histologicalexaminationwithroutinehematoxylin-eosinstaining(Figure, B). Fourteenweeks later thepatientwas seen for follow-up, and the pigmented macules on her lip had substantially regressed without treatment (Figure, C). A second incisional punch biopsy was performed at this time for repeated histological examination. What is your diagnosis?