Endobronchial Mucus Gland Adenoma: A Case Report

Abstract

Abstract Introduction/Objective Mucus Gland Adenoma (MGA) is a rare benign epithelial tumor with few case reports. They arise from submucosal glands and ducts of large proximal airways, but have been reported peripherally and within lung parenchyma. MGAs form an exophytic mass that causes obstructive symptoms, occurring in all ages without gender predilection. MGAs have low to no malignant potential, but may be confused with more aggressive entities. Thus, MGA may present a diagnostic challenge on frozen section. Methods We present the case of a 66-year-old male with recurrent right pneumonia and empyema. Bronchoscopy revealed an obstructing mass in the right bronchus intermedius. Biopsies and cytology were insufficient showing only benign bronchial epithelium. Therefore, the patient underwent surgical sleeve resection of the right bronchus intermedius for diagnosis and treatment. It was received in two pieces measuring 1.0 x 0.6 x 0.5 and 2.0 x 1.5 x 0.9 cm - a well-circumscribed, firm white nodule with a smooth exterior and pushing borders. Cut surfaces were mucoid, homogenous and rubbery, with cysts measuring up to 2 mm. Histology showed crowded mucus-filled acini and tubules lined by bland cuboidal to columnar cells without atypia or mitosis. The stroma showed smooth muscle bundles and lymphocytic infiltrate. Benign bronchial epithelium lined the surface. A preliminary diagnosis of “adenoma” was made, with final classification pending permanent section. Results It showed positivity for s100, CK5/6, and CAM5.2. DOG1 showed a luminal staining pattern. NapsinA was negative and TTF-1 was patchy. P63, P40, CK5/6 and calponin highlighted myoepithelial cells, underlining the benign nature of the process. Conclusion MGA may resemble adenocarcinoma, low-grade mucoepidermoid carcinoma, and other benign adenomas. It presents a diagnostic challenge on frozen section as its malignant differentials are more common. Thus, it is important to recognize and be aware of these rare, benign tumors.