AB045. Mucoepidermoid carcinoma of the lung

Background: To report the case of a male patient, 76, who presented with hoarseness, cough, and hemoptysis. The imaging examinations demonstrated a mass emerging from the trachea wall. A bronchoscopy and tissue biopsy was undertaken. The microscopic examination revealed a case of mucoepidermoid carcinoma of the lung, a rare carcinoma, which belongs to salivary gland-type tumours.

Methods: We received 2 pale-white specimens, 0.8–1.5 cm in greatest diameter. Apart from the hematoxylin-eosin stain, we conducted histochemical and immunohistochemical stains.

Results: The microscopic examination of the tissue revealed a case of a low-grade mucoepidermoid carcinoma. The carcinoma consisted of large squamoid cells with mild to moderate atypia, mainly in a solid pattern of growth with foci of microcystic areas. A small number of scattered mucin-producing cells were distinguishable. Mitoses were rare, while necrosis was absent. The histochemical stains Alcian blue and PAS/PAS D revealed the presence of mucin in the microcystic areas. The neoplastic cells were positive for CK5/6, CK7, p63 and negative for TTF-1.

Conclusions: Mucoepidermoid carcinoma of the lung belongs to salivary gland-type tumours, is a rare entity and accounts for less than 1% of lung carcinomas. It is typically located in the central airways and arises from the minor salivary glands located in the walls of the bronchial tree. It is proposed to be histologically subclassified in low-grade and high-grade type. The characteristic histologic findings involve a mixed cellularity of squamoid cells, mucin-producing cells and intermediate cells, and a lack of keratinization and in situ carcinoma of the overlying epithelium. These findings, as well as the immunophenotype of the neoplastic cells, contribute to the differential diagnosis from adenosquamous carcinoma, adenocarcinoma or squamous cell carcinoma of the lung; a crucial fact, regarding the further differences of these entities in the matter of therapy and prognosis.

Keywords: Immunohistochemical stains; lung mucoepidermal carcinoid; bronchoscopy tissue biopsy