Truly benign "bronchial adenoma". Report of 10 cases of mucous gland adenoma with immunohistochemical and ultrastructural findings.

Mucous gland adenoma of the bronchus (MGAB) is a rare, solitary, benign, well-circumscribed, multicystic, predominately exophytic bronchial tumor. Mucous gland adenoma arises from the submucosal seromucous glands and ducts of proximal airways; since the location, signs and symptoms, and bronchoscopic findings are similar to those of other tumors arising in the bronchus, diagnosis depends on tissue biopsy. We herein report 10 patients with MGAB. Patients ranged in age from 25 to 67 years old (mean, 52). In two thirds of patients, the tumor was located in the middle or lower lobes. Tumors ranged in size from 0.8 to 6.8 cm (mean, 1.8). Cut surface was shiny, mucoid, cystic, and usually firm. Mucous gland adenomas are protean in their histologic patterns. They may appear glandular and tubulocystic or papillocystic, and they often show a mixture of these features. The tumors are rich in mucins and are immunopositive for epithelial markers. Mucous gland adenoma needs to be distinguished from low-grade malignant tumors of the bronchus--most notably, low-grade mucoepidermoid carcinoma. Complete removal of the tumor is curative.