thymoma type B2
Friday 7 December 2012
JRC:3190 : Mixed thymoma Thymoma, B1 (or B2)
Thymoma type B2 (Webpathology)
The tumor is usually located in the anterior mediastinum and myasthenia gravis is the most frequent manifestation. Type B2 thymoma accounts for between 20% to 40% of all thymomas.
Type B2 thymoma is composed of large polygonal tumor cells with vesicular nuclei in a background population of immature T lymphocytes.
There are scattered tumor cells in a background of lymphocytes. The tumor cells have vesicular nuclei with prominent nucleoli. The tumor cells are arranged in loose network, or palisading around fibrous septa or vascular spaces. Large confluent solid sheets of tumor cells are not seen.
High power view showing cytologic features of tumor cells in a Type B2 thymoma. The tumor cells are greatly out-numbered by non-neoplastic lymphocytes.
The biologic behavior of Type B2 thymoma is intermediate between B1 and B3 thymomas. It is often invasive at the time of diagnosis and has higher rate of recurrences and metastases than B1 thymomas.
Perivascular space in a type B2 thymoma. The loose connective tissue in the space contains lymphocytes and a few epithelial tumor cells.