Histopathologic changes in the peripheral lymphoid organs of athymic nude mice transplanted with human tumor

Lymph nodes of tumor-bearing nude mice were evaluated histologically and were found to differ significantly from those of nontumor-bearing control animals. Microscopically, the observed changes wee classified into three patterns, namely histiocytosis, plasmacytosis and formation of germinal centers. The majority of tumor-bearing (63%) showed marked histiocytosis which was either diffuse or nodular involving primarily lymph nodes draining the site of the tumor. Plasmacytosis, affecting lymph nodes at various anatomical sites, was evident in 43% of mice, and in 37% of animals formation of germinal centers was observed. Germinal center formation was always associated with plasmacytosis and markedly increased IgG, IgM and IgA serum levels. There was no repopulation of the thymus-dependent areas by lymphocytes and graft-versus-host reaction was absent.