Unilocular thymic cyst with features of intra-thymic bronchogenic cyst: A clinicopathological correlation of 4 cases.

Four cases of primary unilocular thymic with features of bronchogenic cyst are presented. The patients are three men and a woman between the ages of 43 and 57 years. All the patients presented with symptoms of cough, chest pain, and dyspnea. Diagnostic imaging revealed the presence of an anterior mediastinal cystic lesion. Initial mediastinoscopic biopsies were non-diagnostic. Surgical resection of the anterior mediastinal cystic lesion was performed in all patients. Macroscopically, all the lesions were described as large cystic lesions measuring from 2 to 4 cm in largest diameter and containing yellowish fluid. The surface of the cysts was described as corrugated and of brownish color. The walls of the cysts were not thickened and no other elements were described. Histologically, the cystic lesions were characterized by single cystic structures lined by ciliated epithelium. No atypia or mitotic activity was present in any of the cases. Immunohistochemical stains show positive staining of the respiratory epithelium with keratin and negative staining for GATA3, PAX-8, TTF-1, and Napsin. All the patients have recovered well after surgical resection.