Thymomas with a prominent alveolar growth pattern

Objectives Twelve cases of thymomas with prominent alveolar-like growth pattern are presented. Methods The 12 cases were identified during a review of more than 350 cases of thymomas. Results The patients were five women and seven men between the ages of 48 and 69 years (mean, 58.5 years). Clinically, all patients presented with nonspecific symptoms. Grossly the tumors varied in size from 3.5 to 5 cm in greatest diameter. Histologically, all tumors showed a predominant alveolar-like growth pattern without a significant lymphocytic component. Immunohistochemistry showed positive staining for pan-keratin, keratin 5/6, and p63. Clinical follow-up showed that nine patients have remained alive and well with no recurrence, while no follow-up was obtained in three patients. Conclusions The cases herein described highlight the spectrum of growth patterns that thymomas may show and also highlight the importance to keep thymomas in the differential diagnosis of tumor with prominent alveolar-like growth pattern.