Painful gynecomastia in a patient with malignant thymoma

Gynecomastia is an abnormal increase in the volume of the male breast. This pathological change may occur unilaterally or bilaterally and is generally considered to be due to an increased estrogen/androgen ratio. Gynecomastia is more common in pubertal ages and in older men. Chemotherapy may injure gonadal and hormonal functions and are associated with development of gynecomastia. In this case, a 36-year-old man who had bilateral acute painful gynecomastia associated with malignant thymoma is presented together with a review of the literature. Tamoxifen 20 mg daily was started. Twenty days later, tamoxifen resulted in complete regression of gynecomastia. After an extensive literature search, we found that gynecomastia had not been previously documented in malignant thymoma.