AB044. Adenoid cystic carcinoma of the lung: a rare entity

Background: To report the case of a female patient, 63, who presented with hoarseness, cough and dyspnoe. The bronchoscopy revealed an endobronchial, friable mass in the left main bronchus. The histologic diagnosis was adenoid cystic carcinoma of the lung, a rare entity at this location.

Methods: Firstly, we received bioptic tissue material, following bronchoscopy, and, secondly, a surgical resection was undertaken, involving a part of the trachea (3 cm in length) and of the main bronchus (4 cm in length), as well as 4 adjacent lymph nodes. We performed hematoxylin-eosin, and immunohistochemical stains.

Results: The microscopic examination revealed a case of an endobronchial carcinoma, with small to medium-sized cells, containing little cytoplasm and oval, deeply-stained nuclei, in tubular, cribiform, or solid patterns, within an hyalinized, often myxoid stroma. Perineural invasion was frequent, while mitoses were rare. The carcinoma was covered with normal bronchial epithelium, infiltrated the cartilage of the bronchial wall and grew outwards, infiltrating the peribronchial fat tissue, as well as 2/4 adjacent lymph nodes. The neoplastic cells stained positively for CK7, CK8/18, CK5/6, p63, and negative for TTF-1. The rest of the surgical specimens of the trachea and lymph nodes were malignancy-free.

Conclusions: Adenoid cystic carcinoma is a malignant epithelial tumor, located typically in the salivary glands, while the primary location in the lung is rare, accounting for only <0.04–0.2% of lung malignancies. Because of its rarity and submucosal location, patients are usually falsely treated for asthma or chronic obstructive pulmonary disease, resulting in delayed treatment of the carcinoma. The typical morphology consists of small to medium-sized cells, in a tubular, cribiform or solid pattern of growth, rare mitoses and frequent perineural invasion. Cytokeratins and p63 are expressed positively, while there is a lack of TTF-1 expression; findings, which will guide the differential diagnosis from lung adenocarcinoma. It is equally important to rule out metastasis from other organs.

Keywords: Lung cystic; adenoid cystic carcinoma; immunohistochemical stains