[A case of lung cancer showing a bronchial cast shadow caused by impaction of the squamous cell carcinoma itself].

A 69-year-old man presented with bloody sputum. Chest X-ray showed a trabecular shadow in the right upper lung field. Chest CT showed a bronchial cast shadow in the right B3a, extending along the bronchial bifurcations to the periphery. Impaction of the bronchus was suspected. Sputum cytology was class IIIb. Though bronchoscopic examination did not reveal a tumor or obstruction at the orifice of the right B3a, squamous cell carcinoma was diagnosed by biopsy. Right upper lobectomy was performed. Pathologically, the tumor was diagnosed as moderately differentiated squamous cell carcinoma, measuring 25 x 20 x 10mm in size. The tumor showed intrabronchial branching growth into the peripheral site of the right B3a and neither mucoid nor inflammatory granulation tissue was present. Impaction of the bronchus was made up by the squamous cell carcinoma itself. Lung cancer originating in subsegmental or sub-subsegmental bronchi, showed bronchial cast appearance due to intrabronchial growth is very rare.