Granular cell myoblastoma of the lung.

Three cases illustrate the principal clinical and roentgenographic varieties of granular cell myoblastoma (GCM) of the lung. The vast majority are small benign intrabronchial tumors without roentgenographic findings. These remain asymptomatic and are detected accidentally at autopsy, surgery, or bronchoscopy (Case III). Larger obstructing lesions (Case I) cause focal atelectasis or pneumonitis, leading to cough, expectoration, and hemoptysis. Hilar enlargement from reactive lymph node hyperplasia is common. Clinically and roentgenographically these are indistinguishable from bronchial adenomas. Least often the tumor extends entirely extrabronchially (Case II) presenting as a parahilar parenchymal asymptomatic nodule, simulating a granuloma, hamartoma, arteriovenous malformation or a neoplastic nodule.