Objective: According to a computerized medline search in the English literature, the present case is thought to be the first primary pulmonary adenocarcinoma with enteric differentiation, completely resembling metastatic colorectal adenocarcinoma morphologically, with a history of metastatic colon adenocarcinoma. Results: A 62 year old man with a history of colon adenocarcinoma which was detected in 2007 underwent radiologic evaluation. A chest computed tomography scan revealed a 7 mm solitary nodule in the left lower lobe which enlarged in 1 year. The patient underwent left lower lobe wedge resection. Macroscopically, an irregular whitish nodule of 1.5 cm in greatest diameter was detected. Microscopically, the nodule was entirely composed of glandular and papillary structures, some of which had a cribriform pattern, lined by tumor cells that were cuboidal to tall columnar with nuclear pseudostratification, eosinophilic cytoplasm, brush-border, luminal necrosis and nuclear debris. Tumor cells were diffusely positive for cytokeratin (CK)7 and negative for thyroid transcription factor-1, surfactant protein-A, CDX-2 and MUC2. Only a very few tumor cells stained for CK20. Conclusion: Enteric morphology with consistent expression of CK7 and a scattered positivity for CK20 helped in the distinction from metastatic colon adenocarcinoma and favored the diagnosis of primary pulmonary adenocarcinoma with enteric differentiation.