2018 Volume 40 Issue 6 Pages 584-589
Background. Pulmonary enteric adenocarcinoma, a rare variant of primary invasive adenocarcinoma of the lung, can be difficult to distinguish from pulmonary metastasis of colorectal cancer. Case. A man in his 70s was referred to our hospital because of an abnormal shadow observed on chest X-ray. Chest CT revealed a lobulated small nodule which was located in the pulmonary right upper lobe, measuring 21 mm on the longitudinal axis. The transbronchial biopsy specimens of the pulmonary nodule pathologically demonstrated that the tall and columnar tumor cells were composed of oval nuclei and dense chromatin. Immunohistochemical investigation revealed that the tumor cells were positive for cytokeratin (CK) 20, and negative for thyroid transcription factor-1 and CK7; these results suggested that this tumor was pulmonary metastasis from colorectal cancer. PET/CT demonstrated that the right pulmonary nodule and the lesion in the ascending colon had abnormal FDG uptake. Total colonoscopy showed a polypoid lesion in the ascending colon, which was pathologically confirmed to be a low-grade tubular adenoma. According to the diagnosis of primary pulmonary adenocarcinoma cT1bN0M0 (General Rules for Clinical and Pathological Records of Lung Cancer (GRLC), 7th edition), right upper lobectomy was performed via video-assisted thoracoscopic surgery. The immunohistochemical findings of the surgically resected specimens were similar to those of the transbronchial biopsies. The pathological final diagnosis was primary pulmonary well-differentiated adenocarcinoma, acinar-type pT1aN0M0 (GRLC 7th edition), which was clarified as enteric adenocarcinoma according to the GRLC 8th edition. Conclusion. Total colonoscopy is mandatory to distinguish pulmonary enteric adenocarcinoma from pulmonary metastases of colorectal cancer in case of failure of pathological confirmation.
