In Situ Melanoma of the Gingiva Associated with Dense Inflammation and Pigment Deposition: A Potential Diagnostic Pitfall in Evaluating Stromal Invasion.

Melanoma is a highly aggressive neoplasm in which the neoplastic cells display melanocytic differentiation. Less than 1 % of all melanomas arise in the mucosal surfaces of the oral cavity, with purely in situ lesions being exceedingly rare tumors, but with a favorable prognosis compared with invasive lesions. We describe the clinical, histopathological and immunohistochemical findings in an uncommon case of in situ mucosal melanoma of the oral cavity with intense tumor-associated pigment deposition and inflammation complicating the morphological assessment of infiltrative areas.