Abstract
Colonic metastasis from lung cancer is rare and generally asymptomatic. Here, we report a case with lung adenocarcinoma that presented with acute abdominal pain due to intestinal obstruction caused by the metastatic colon tumor. The patient underwent emergency colonoscopy and the pathologic report was adenocarcinoma, which was the same as that for a bronchoscopic biopsy from a large lung mass. Immunohistochemistry was positive for thyroid transcription factor-1 and cytokeratin 7, and negative for cytokeratin 20 and caudal-related homeobox transcription factor 2 on both lung biopsy and colon surgical specimens. Accordingly, we used immunohistochemistry for thyroid transcription factor-1, cytokeratin 7, cytokeratin 20 and caudal-related homeobox transcription factor-2 to diagnose primary adenocarcinoma of the lung with colonic metastasis.