Delayed Endobronchial Metastasis of Colorectal Adenocarcinoma Five Years After Resection: A Case Report.

Endobronchial metastasis (EBM) is a rare manifestation of extrapulmonary malignancies and poses a diagnostic challenge because it can closely mimic primary bronchogenic carcinoma. Although colorectal carcinoma (CRC) is among the most common malignancies worldwide, endobronchial involvement is distinctly rare and represents an atypical pattern of metastatic dissemination. We present the case of an 83-year-old woman with a history of resected KRAS-mutant sigmoid adenocarcinoma who developed symptomatic near-complete endobronchial obstruction more than five years after complete resection by colectomy. Imaging demonstrated presumed widespread multiorgan metastatic disease, including a large left upper lobe mass, mediastinal lymphadenopathy, hepatic and adrenal lesions, vertebral lytic lesions, and bilateral pulmonary nodules. Bronchoscopy revealed an exophytic mass in the left mainstem bronchus, causing near-complete luminal obstruction. Multimodal endoscopic debulking using a cautery snare, argon plasma coagulation (APC), and laser ablation successfully restored airway patency. Histopathology confirmed moderately differentiated metastatic colonic adenocarcinoma with CK20 and CDX2 positivity. This case highlights that CRC can recur with aggressive dissemination to rare metastatic sites even after complete surgical resection. Furthermore, loss to follow-up in high-risk patients may permit undetected disease progression, supporting a more individualized approach to long-term surveillance. Imaging alone may fail to detect endobronchial disease, making early bronchoscopy essential for timely diagnosis and management.