Light micrograph of a section of a human trachea showing a tracheobronchial tumour. This rare tumour can occur in both children and adults. They are usually benign in children but malignant in adults. The most common forms of tracheobronchial tumours include squamous cell carcinoma, adenoid cystic carcinoma, carcinoid tumours, chondromas, haemangiomas and papillomas. Symptoms include pneumonia, weight loss and trouble swallowing.