Pseudocystic Condition of Lymph Nodes in C57BL Mice

In a colony of a substrain of C57BL mice bred for 6 years, many cases of ectatic transformation of superficial lymph nodes were observed. The pseudocysts that developed in this way did not produce any alteration in the general state of health; their presence was compatible with long survival. Histogenetic study showed that the cysts always developed from the central sinuses and that their occurrence did not seem related to a change in the lymphatic flow through the efferent vessels. At the precystic stage, the lymph nodes exhibited a degenerative process of the reticular cells, especially in the hilar region; a marked rise in the number of mast cells which were more or less degranulated; and some megakaryocytes. The pseudocystic condition of nodes was more frequent in females than in males. Among 220 females, 40 (17%) had pseudocysts; among 154 males, only 9 (6%) had them. The average latency for both sexes was approximately 14 months. The injection of the cystic fluid into mice of other strains did not produce such ectatic changes. In newborn C57BL mice, it did not induce precocious appearance of cysts. The occurrence of the lesions did not seem related to senility.