Abstract
Pulmonary enteric adenocarcinoma (PEAC) is a rare subtype of non-small cell lung cancer with morphological and immunohistochemical features that are nearly indistinguishable from those of metastatic colorectal carcinoma. Owing to these overlapping features, diagnosis and treatment of PEAC can present a clinical challenge. We report the case of a 78-year-old man with synchronously diagnosed locally advanced pulmonary adenocarcinoma of the left lower lobe and localized right lower lobe PEAC. These malignancies exhibited distinct tumor molecular profiles and differed in their kinetic response to chemoimmunotherapy. We describe plausible mechanisms by which two distinct pulmonary malignancies are present in the contralateral lobes. To the best of our knowledge, this is the first reported case of synchronous invasive pulmonary adenocarcinoma and PEAC.