Origin of Metastatic Colonic Adenocarcinoma Suspected from a Primary Lung Cancer: A Case Report and Literature Review

Abstract

Lung cancer with gastrointestinal metastasis is uncommon; however, when such metastasis occurs, the small bowel is the most common metastatic site. There are few case reports of colonic metastasis developing from a primary lung adenocarcinoma. We report a case of metastatic adenocarcinoma in the colon, complicated by bowel obstruction and hydropneumothorax, in a 67-year-old woman. The primary cancer was highly suspected to have originated from the lung, based on immunohistochemistry assessments. Immunohistochemistry was positive for thyroid transcription factor-1 and cytokeratin 7, but negative for cytokeratin 20. The published literature, focusing on the differential diagnosis of the origin of the primary malignancy using immunohistochemistry, was reviewed.