Mixed lung mucoepidermoid carcinoma and adenocarcinoma with identical mutations in an epidermal growth factor receptor gene.

Lung cancers presenting two different histologic types are relatively rare. This paper presents a case report of mixed lung cancer comprising mucoepidermoid carcinoma and conventional adenocarcinoma, a combination that has not been reported previously. These two carcinomas showed distinct morphologic and immunohistochemical features. However, gene analysis revealed identical mutations in each component, which indicates they possess a monoclonal origin. Specifically, we identified the same mutation in exon 19 of the epidermal growth factor receptor gene. Molecular analysis further substantiated a monoclonal origin with divergent differentiation, as opposed to the collision of discrete tumors.