The clinical presentation and the CT features are suggestive of thymoma, biopsy proven as thymoma type B1.

There are five main histologic subtypes of thymomas:

1. type A: medullary thymoma

2. type AB: mixed thymoma

3. type B1: predominantly cortical thymoma

4. type B2: cortical thymoma

5. type B3: well-differentiated thymic carcinoma