Differential diagnosis of an oral mucosal pigmented lesion: a case of essential melanosis

Introduction: The presence of a pigmented lesion of the oral mucosa raises numerous diagnostic hypotheses. The INCa (National Cancer Institute) considers “any pigmented lesion of the oral mucosa as a melanoma until proven otherwise.” A histological confirmation is thus necessary. Clinical observation: A 64-year-old female patient consulted for a pigmented lesion of the marginal gingiva of 11 and 21, corresponding to a single round macule of approximately 0.5 cm diameter, brown, homogeneous, covered with a slight keratinization, with regular edges. The rest of the clinical examination was unremarkable. An excisional biopsy confirmed the diagnosis of essential melanosis or Laugier–Hunziker syndrome. Discussion: Pigmented lesions may occur in an isolated form or may be a component of major syndromes. Unique pigmentation of the oral mucosa can be of endogenous origin (e.g., malignant melanoma, essential melanosis, lentigo, different nevi) or of exogenous origin (e.g., ethnic pigmentations, metallic or medicinal origin, vascular lesions, and neuroectodermal tumor in children). Conclusion: Although rare at the gingival level, essential melanosis must be considered in the differential diagnosis of a single flat lesion. Nevertheless, melanoma should always be ruled out, and its early diagnosis is the only favorable prognostic factor in its evolution