Imaging of an invasive malignant thymoma on PET scan: CT and histopathologic correlation

Thymomas are common primary mediastinal neoplasms. They can be benign or malignant. The diagnosis of malignant thymomas is based on capsular invasion, cellular atypia and distant metastases. We present a case of invasive malignant thymoma as diagnosed on PET and CT scan with histologic correlation and review of literature. A seventy year old Asian man presented with cough and dyspnea. A CT scan showed an anterior mediastinal mass, and a PET scan showed a hypermetabolic mass in the corresponding location. Resection of the mass revealed a minimally invasive thymoma based on evidence of capsular invasion. PET scan proved invaluable in correctly diagnosing, staging the lesion, and excluding any extramediastinal involvement.