56 year old man with remote history of malignancy presents with pleuritic and ill-defined chest pain.
Enhancing mass “stuck on” the left pericardium. Normal left ventricular wall motion.
Recurrent thymoma
Recurrence of invasive thymoma and thymic carcinoma often presents with pleural and pericardial implants.
WHO Classification of Thymic Epithelial Tumors
(simplified version)
WHO Type A
Histology: Spindle-shaped thymic epithelial cells without nuclear atypia, absent nonneoplastic lymphocytes (A) or foci of nonneoplastic lymphocytes (AB)
Imaging: Well-defined lobulated mass with smooth margins, mild FDG uptake
PET/CT images
WHO Type B
Histology: Range from normal thymic cells (B1) to round cells with distince nucleoli (B3), nonneoplastic immature lymphocytes
Imaging: Mass with poorly defined margins, +/- calcification, moderate-intense FDG uptake.
PET/CT images
Post contrast MRI images
WHO Type C (Thymic Carcinoma)
Histology: Atypical cells with differentiation similar to squamous, lymphoepithelial, or other carcinomas
Imaging: Mass with poorly defined margins or invasion of mediastinal fat, lymph node metastasis, intense FDG uptake
PET/CT images
FDG uptake correlates with WHO type/aggressiveness
References / Further Reading:
Sung YM, et al. J Nucl Med 2006;47:1628-1634.
ITMIG Discussion of WHO Classification