Primary Warthin's-like adenocarcinoma of the lung: A clinicopathological, immunohistochemical, and molecular analysis of three cases.

Three cases of primary pulmonary adenocarcinoma with prominent lymphoid stroma and papillary features mimicking Warthin's tumor are presented. The patients are two women and one man ages 52, 62, and 74 years respectively. Clinically, the patients presented with non-specific symptoms of cough, dyspnea, and chest pain. Imaging showed the presence of an intrapulmonary mass in the right lower, right upper and left lower lobe. All patients underwent lobectomy. Histologically, the tumors were characterized by the presence of and oncocytic papillary growth pattern embedded in a lymphoid rich background. Immunohistochemical stains for TTF-1, keratin 7, and beta-catenin were positive in the epithelial component, while CD20 showed strong positive staining in the lymphoid component. In addition, CD4 and CD8 also showed positive staining in a ratio of 3-4:1, EBER was negative. Kras mutations with wild type EGFR were identified in one case. Clinical follow-up ranging from 8 to 24 months was obtained showing that all patients are alive without recurrence. The cases herein presented represent an unusual histological variant of primary lung adenocarcinoma, which closely mimics Warthin's tumor.