After examination of 150 female quails, four of them showed the dedifferentiate tumor of the bursa of Fabricius. To the periphery, it consists of the dedifferentiate hemangiosarcoma and liposarcoma, the predominant area being constituted from lymph nodes of variable sizes. Among the lymphocytes rows the extensions of the reticular cells appeared positive for MHC II antibody. The lymphocytes showed the negativity to p53. The Bcl-2 marker manifested a limited positive reaction only in certain follicles. IgA and IgM markers showed the relatively low level of positivity in lymph nodes. Only the dense cords of the pleomorphic melanocytes manifested the positivity to Bcl-2. At the junctions between ventriculus and duodenum; ileum and cecum, especially in serosa, there were identified lymphocytes positive to MHC II, Bcl-2 and p53 markers surrounded by clusters of lipoid cells located inside the intestine wall. These structures were metastases of the dedifferentiate tumor of the bursa of Fabricius.

Key words: Bursa of Fabricius, Dedifferentiate tumor, Hemangiosarcoma, Immunohistochemistry, Liposarcoma, Quail