Colon carcinoma with endobronchial metastasis masquerading as bronchial asthma causing ball valve effect.

Malignant central airway obstruction (CAO) with ball valve effect (BVE) in the lung is rare. We discuss a case of metastatic colon cancer who presented with asthma like symptoms which thoracic computed tomography and bronchoscopy revealed an intraluminal tumour obstructing the left main bronchus in a ball valve manner. Airway patency was restored urgently with immediate alleviation of symptoms. This illustrates the importance of recognizing subtle features of central airway obstruction to allow expedition of appropriate investigations and therapy.