Analysis of human omentum-associated lymphoid tissue components with S-100: an immunohistochemical study

Milky spots are opaque patches in the greater omentum. They were first described by von Recklinghausen (1863) in the omentum of rabbits. In man, milky spots are relatively uniform, highly vascularized accumulations of mononuclear cells. The objective of this study was to describe in human omental lymphoid tissue components with S-100. Tissue samples (greater omentum) were collected from 14 patients operated with different reasons in our Department of General Surgery, in order to histologically present the presence of S-100 in the cells making up the milky spots in human omentum tissue. Tissue samples were cut approximately 5-8 micrometer thick with frozen-sections and stained with an indirect immunoperoxidase technique, as described previously. Then milky spots were examined by light microscopy. These data indicate that unstimulated milky spots in the human greater omentum are to a great extent just a preformed specific accumulation of primarily macrophages within the stroma of the greater omentum, secondarily B- and T-lymphocytes. In addition to these cells, we observed that a few mast and reticular cells were seen in the milky spots by S-100 reactive cross-sections of greater omentum. In the human omentum tissue that was stained with indirect immunoperoxidase method using anti S-100 monoclonal antibody, an arteriole cross-section in the center, reactive nerve cross-sections in the adjacent stroma and endogenic peroxidase reactivity in a few granulocytes in omental tissue were observed.