Fig. 20.

Stage IVa thymoma (WHO type B2) in a 46-year-old man. a Contrast-enhanced CT scan reveals an anterior mediastinal mass (arrows) with irregular contours, homogeneous enhancement and peripheral and central calcification as well as a pleural nodule (open arrow). b On an axial FDG-positron emission tomography (PET) image, the pleural nodule is FDG avid, confirming a drop metastasis. c Image during the surgical resection. d Photomicrograph (haematoxylin-eosin stain) of tissue from the lesion shows roughly equal numbers of epithelial cells (white arrow) and lymphocytes (black arrow) corresponding thymoma WHO type B2