Endobronchial Metastasis as the Dominant Pulmonary Manifestation of Sigmoid Colon Adenocarcinoma: A Case Report

Pulmonary metastases from extrapulmonary malignancies are common; however, when a patient with a history of colorectal cancer develops new respiratory symptoms, clinicians typically look to the lung parenchyma for pulmonary metastases and rarely to the airway itself. Endobronchial metastases (EBM) occur when tumor deposits are confined to the bronchial epithelium and airway lumen rather than the surrounding lung tissue. This represents a distinct and often overlooked pattern of spread, and those originating from colorectal cancer are especially uncommon. This report presents a case of a 60-year-old man with sigmoid colon adenocarcinoma and synchronous peritoneal metastasis (TNM stage M1c), treated with colectomy followed by adjuvant FOLFOX chemotherapy for approximately one month. Approximately two weeks after completing the first chemotherapy cycle, he developed progressive dyspnea, dry cough, dizziness, and fatigue. Chest imaging demonstrated multiple bilateral pulmonary nodules and opacities concerning for multifocal pneumonia versus lymphangitic carcinomatosis with possible endobronchial involvement, and he developed hypoxemia requiring supplemental oxygen. Despite empiric antibiotic therapy for presumed pneumonia, his symptoms persisted, prompting bronchoscopy with endobronchial and transbronchial biopsy, which revealed endobronchial lesions in the lingula and right middle lobe. Histopathology and immunohistochemistry (CDX2-positive, CK7-negative, and TTF-1-negative) were consistent with metastatic colorectal adenocarcinoma. Despite multidisciplinary management, his respiratory status progressively deteriorated, and he died of refractory respiratory failure. This case underscores that EBM should be considered in any oncology patient with persistent respiratory symptoms and pulmonary lesions, even without a parenchymal mass, and that bronchoscopy with biopsy remains the diagnostic gold standard for distinguishing EBM from primary lung cancer, sarcoidosis, and infection, and for guiding prognosis-directed and palliative management.