A 70-year-old man was referred to our department due to abnormal shadows on a chest radiograph. Computed tomography of the chest revealed a 3-cm nodule in the right middle lung lobe, and bronchoscopy revealed adenocarcinoma cells with EGFR mutations. A lung resection was performed. Histological analysis revealed tumors comprising tall columnar cells that were similar to an adenocarcinoma of the sigmoid colon that had been resected 13 years previously. Metastatic colorectal carcinoma was initially considered, but immunohistochemical staining indicated pulmonary enteric adenocarcinoma. Pulmonary enteric adenocarcinoma was first described in 1991, and about 30 cases have since been described in the English literature. However, its concept and etiology are not clear. It is important to distinguish pulmonary enteric adenocarcinoma from metastatic colorectal carcinoma because of obvious differences in therapeutic strategies and prognosis, especially with a past history of colorectal carcinoma. Immunohistochemical and gene mutation analyses seemed to be helpful.
Keywords: Enteric adenocarcinoma; Immunohistochemical staining; Lung cancer; Metastatic colorectal carcinoma.