Immunomorphologic lymph node changes in rats bearing experimental breast tumors

In this paper regional lymph nodes draining tumors and also nonregional lymph nodes have been studied at the light- and electron-microscopic levels. These nodes were obtained from rats bearing long-evolving autochthonous breast cancers. They were compared with a control group of the same age. A morphometric quantitative analysis was done to evaluate immunologically competent cell populations. In the experimental group there were no differences between regional and distal lymph nodes in the tumor challenge. However, when the experimental group was compared with the control group, differences appeared. The changes involved were diminution of the paracortical area with stimulation of plasma cells in the medullary cords. Ultrastructurally, in lymph nodes of the experimental group there were lymphoblasts in the paracortex and germinal centers, suggesting active lymphopoiesis. In addition, many plasma cells showed morphologic evidence of involution or other alterations. It is suggested that regional and distal lymph nodes have similar morphologic behavior when the tumor grows for a long period of time, a finding that contributes to our knowledge of the systemic implications of the lymphatic system.