Mixed mucoepidermoid carcinoma and adenocarcinoma of the lung: Two cases with unusual histologic features

We herein report two cases of non-small cell lung cancer with unusual histologic patterns, comprising mixed mucoepidermoid carcinoma and adenocarcinoma. Both cases presented identical genetic mutations in each histologic component of the tumor; specifically, one case possessed an ALK-rearrangement and the other case presented a deletion in exon 19 of the EGFR gene. The two current cases, as well as an additional case that we previously reported, were all identified as being a specific type of mixed lung cancer with driver mutations typically encountered in conventional lung adenocarcinomas. Our findings support the supposition that different histological components in mixed-histology lung cancer are clonally related. Accordingly, extensive tissue sampling is necessary to avoid overlooking minor adenocarcinomatous components, as patients with mixed lung cancer could potentially benefit from treatment with tyrosine kinase inhibitors.