Thymomas with prominent glandular differentiation: a clinicopathologic and immunohistochemical study of 12 cases

Twelve cases of thymomas with prominent glandular differentiation are presented. The patients were 7 men and 5 women aged between 45 and 68 years (average, 56.5 years). Clinically, the patients presented with nonspecific symptoms of chest pain, cough, and fatigue. None of the patients had a history of myasthenia gravis or other autoimmune syndrome. Thymectomy was performed in all patients. The tumor size ranged from 4 to 7 cm in greatest diameter. Macroscopically, the tumors were described as firm and light tan without areas of necrosis, hemorrhage, or cystic change. Histologically, 7 tumors were classified as spindle cell (World Health Organization type A), 2 as mixed spindle cell and conventional (A+B1), 2 as conventional (B1), and 1 as atypical thymoma (B3). In 4 cases, the tumors showed invasion into periadipose thymic tissue. All cases showed the typical growth patterns of their particular subtypes. In addition, a distinct glandular component was present in all cases showing mucinous differentiation in 4 of them. Immunohistochemical studies showed tumor cells positive for CAM5.2, cytokeratin 5/6, and Pax8 and negative for carcinoembryonic antigen, thyroid transcription factor 1, and epithelial membrane antigen. Calretinin showed focal weak staining in the nonmucinous glandular components in 3 cases. Follow-up information obtained in 8 patients showed that all were alive and well in a period ranging from 2 to 5 years. The possibility of a glandular component in thymomas should be kept in mind in the assessment of mediastinoscopic biopsies to avoid misdiagnosis for Other neoplasms that may require different treatment modalities. (C) 2013 Elsevier Inc. All rights reserved.