Incidence of spontaneous non-neoplastic lesions of lymphoid organs in Wistar rats

The incidence of spontaneously occurring pathological lesions in various lymphoid organs was studied in Wistar rats aged about 19–21 weeks. A total of 596 rats (male-298 and female-298) contributed the morbid material. Lymphoid tissues from all the animals were routinely collected for evaluation of potential pathological lesions. Based on gross and histopathological studies the rate of occurrence was determined. The most common lesions in spleen were congestion/hemorrhage (11.41%), extra medullary hematopoiesis (4.87%), hemosiderosis (5.70%), atrophy (6.88%), lymphoid hyperplasia (7.21%) and fibrosis (0.67%). In thymus, commonly observed lesions included atrophy/lymphoid depletion (10.91%), epithelial cell hyperplasia (4.36%), starry sky appearance (4.19%), congestion/haemorrhage (3.02%), histiocytosis (0.34%), lymphoid hyperplasia (3.69%), cyst (0.34%) and hemosiderin deposition (0.34%).Various lymph nodes revealed lesions like atrophy/lymphoid depletion (3.02%), congestion/haemorrhage (0.34%), hemosiderin deposits (1.85%), fibrosis (2.35%), sinus histiocytosis (6.04%) and lymphoid hyperplasia (11.74%). A variety of other less commonly lesions was also identified in both the sexes of rats.