Colon Metastasis From Primary Lung Cancer: A Report of a Rare Case and Review of Diagnostic and Therapeutic Challenges.

This case report aims to describe the rare occurrence of colon metastasis that originated from primary lung adenocarcinoma, highlighting the diagnostic challenges, therapeutic interventions, and clinical implications. A 62-year-old woman diagnosed with a biphenotypic lung carcinoma (squamous and adenocarcinomatous components) developed gastrointestinal (GI) symptoms. Imaging and endoscopic evaluation revealed a 3 cm sessile polypoid lesion in the ascending colon. Histopathological analysis and immunohistochemical profiling confirmed the lesion as a metastatic adenocarcinoma from the primary lung cancer. The patient underwent successful endoscopic mucosectomy with clear surgical margins, followed by targeted therapy with osimertinib due to the presence of an epidermal growth factor receptor (EGFR) mutation. Thus, this case underscores the necessity of considering metastatic lung cancer in the differential diagnosis of colonic lesions, particularly in patients with a known history of lung cancer. Comprehensive histopathological and immunohistochemical analyses are crucial for accurate diagnosis. The management of such rare metastases requires a multidisciplinary approach, integrating surgical and targeted therapies to improve patient outcomes. This report adds valuable insights into the clinical presentation, diagnostic processes, and therapeutic strategies for atypical metastatic patterns in lung cancer.