Labial melanotic macule: a clinical, histopathologic, and ultrastructural study.

Abstract

The labial melanotic macule (LMM) is a recently described pigmentary anomaly that may simulate malignant melanoma. Our purpose was to define the LMM clinically, histologically, and immunohistochemically in a large group of patients. We describe the clinical features of 36 LMMs in 29 patients (aged from 4 to 79 years, 4 male, 25 female) seen during the past 4 years. Histopathologic findings in 21 of these patients are discussed. Seventeen lesions were immunostained with HMB-45 monoclonal antibody, and electron microscopy was performed on eight lesions. The majority of patients were women and had solitary lesions on the lower lip with the mean age of onset of 30 years. Histologically prominent basilar hyperpigmentation accentuated at the tips of the rete ridges was present without atypia or nevoid formation. Immunohistochemical studies showed that all intralesional melanocytes were HMB-45 negative, supporting their benign nature. Ultrastructurally, numerous stage III and IV melanosomes clustered within basal keratinocytes and papillary dermal melanophages were found. The LMM is a clinically and histologically distinctive benign pigmentary anomaly.