Collision tumor consisting of primary mucoepidermoid carcinoma and adenocarcinoma in the lung: a case report and literature review.

Mucoepidermoid carcinoma in the lung is uncommon, while the occurrence of a collision tumor consisting of primary mucoepidermoid carcinoma (MEC) and typical adenocarcinoma is extremely rare. We report a case of a 70-year-old female with the presence of a nodule in her right lung. The pathological examination revealed a primary collision tumor consisting of invasive adenocarcinoma and mucoepidermoid carcinoma. Manual microdissection was performed to selectively isolate the MEC and adenocarcinoma components, followed by exome sequencing which unveiled identical mutations in both components, suggesting their monoclonal origins with divergent differentiation. Clinical awareness and recognition of such collision tumors are crucial, as they will determine appropriate treatment strategies based on the individual biological aggressiveness of each tumor component.