Endobronchial Metastasis of Sigmoid Colon Adenocarcinoma: A Case Report

A case report published in the journal Cureus describes a rare instance of sigmoid colon adenocarcinoma where endobronchial metastasis served as the dominant pulmonary manifestation. In this specific clinical presentation, the cancer spread from the colon to the bronchial tubes of the lungs, causing obstructive symptoms that preceded the discovery of the primary tumor in the colon.

According to the report, this pattern of metastasis is uncommon. Colorectal cancer typically spreads to the lungs via hematogenous routes, resulting in multiple small nodules throughout the lung parenchyma. Endobronchial spread, where the tumor grows within the airway itself, is a significantly rarer occurrence.

Clinical Presentation of Endobronchial Metastasis

The patient in the Cureus case report presented with respiratory symptoms that pointed toward an airway obstruction. This differs from the typical presentation of lung metastases, which often remain asymptomatic until they are numerous or large enough to impair overall lung function.

In this case, the endobronchial growth acted as the primary indicator of advanced malignancy. The report notes that the tumor’s location within the bronchus can lead to symptoms such as hemoptysis, persistent cough, or localized lung collapse (atelectasis) due to the blockage of airflow to specific sections of the lung.

Diagnostic imaging and subsequent bronchoscopy were used to identify the mass within the airway. Biopsy and histological examination confirmed that the pulmonary mass was an adenocarcinoma originating from the sigmoid colon, rather than a primary lung cancer.

Pathways of Colorectal Cancer Spread

Medical literature generally classifies the spread of colorectal cancer into several patterns. According to the Cureus report, the most frequent pulmonary manifestation is the development of multiple parenchymal nodules. This occurs when cancer cells travel through the bloodstream and lodge in the lung tissue.

Endobronchial metastasis represents a different mechanism. While the exact pathway for this specific type of spread is less common, it results in a tumor that obstructs the bronchial lumen. This creates a clinical picture that can mimic primary bronchogenic carcinoma, potentially leading to diagnostic challenges if the patient’s gastrointestinal history is unknown.

The report emphasizes that the sigmoid colon is a frequent site for primary adenocarcinomas, which are malignant tumors forming in the glandular structures of the colon lining.

Diagnostic and Therapeutic Implications

The discovery of endobronchial metastasis requires a multidisciplinary approach to diagnosis. Because the symptoms are respiratory, the report indicates that clinicians may first suspect primary lung cancer. However, immunohistochemical staining is used to differentiate the origin of the cells.

Markers such as CK20 and CK7 are often utilized in these cases. A positive CK20 and negative CK7 result is typically indicative of a colorectal origin, whereas the opposite pattern is more common in primary lung adenocarcinomas.

Treatment for metastatic sigmoid colon adenocarcinoma generally involves a combination of systemic chemotherapy and targeted therapies. In cases where endobronchial obstruction causes severe respiratory distress, local interventions such as bronchoscopic debulking or stenting may be considered to maintain airway patency, though these are palliative rather than curative.

The Cureus case report serves as a clinical reminder that respiratory symptoms can be the first sign of an occult gastrointestinal malignancy, necessitating a thorough systemic search for a primary tumor when unusual pulmonary masses are identified.