Type B2 Thymoma : Gross
Type B2 thymomas may be totally encapsulated (Stage I; one-third of cases) or show (in the remaining two-thirds of cases) microscopic or macroscopic invasion of mediastinal fat (Stage II) or invasion of adjacent structures such as lung, pleura, or pericardium (Stage III). The cut surface is grey-white and divided into lobules by fibrous septa. Areas of necrosis, hemorrhage, or cystic change may be seen. Image courtesy of Dr. Jean-Christophe Fournet, Paris, France; humpath.com; Used with permission.