An autopsy case of a giant mesenteric lymphoid tumor in a 57-year-old female was examined anatomo-biologically. A 17X15X6 cm3-sized pinkish gray-coloured medullary tumor occupying the mesenterium with no evident capsule, invaded the small intestine and pancrease head. Histologically, it was a lymphoid tissue consisting of hyalinized angiofollicular architecture having epithelioid cells and tingible body macrophages in the follicles. Some small-sized follicles showed typical Hassalloid architecture and other follicles consisted of monotonous growth of lymphocytes without a mantle zone, some of them fusing with each other. The histopathological appearance of the tumor was that of Castleman's lymphoma and of hyaline-vascular type of Keller's Classification. There was another 0.6X0.5X0.5 cm3-sized tumor having an angiofollicular architecture in the subserosa of the sigmoid colon. The present case was complicated with vertebral caries, hypogammaglobulinemia (1.2%), eosinophilia (50%) and panbronchobronchiolitis, the last one being responsible for her death.