Spleen - Accessory Spleen

Accessory spleens (Figure 1, arrow) are rare findings in rodents and may be congenital, acquired following splenectomy, or a consequence of traumatic injury. When observed grossly in the peritoneal cavity, an accessory spleen may appear as one or more dark red to black nodules that have a smooth surface and range from less than a millimeter to several millimeters in diameter. These small nodules of splenic tissue have been observed in the mesenteric attachment of the spleen (Figure 1, arrowhead), pancreas, and elsewhere in the abdominal cavity. Histologically, accessory spleens may have all or some splenic components, such as the capsule, trabeculae, red pulp, and/or white pulp (Figure 2).