Mobile encapsulated bodies comprising fat necrosis and fibrous tissue in the abdominal cavity of cows.

The microscopical features of 18 samples of fat necrosis and/or fibrous tissue removed from the abdominal cavity during laparotomy from 15 cows were studied. The nodular, ivory-coloured mobile structures were free-floating in the abdominal cavity, were not attached to any abdominal tissues or organs, and were completely surrounded by a fibrous capsule. Abdominal fat necrosis (bovine lipomatosis) was not observed in any animal. The structures comprised either necrotic fat, fibrous tissue or varying proportions of both. Focal calcification and mild inflammatory cell infiltration and accumulations of haemosiderin were also present. Microscopically, the lesions resembled encapsulated fat necrosis occurring in human subcutaneous tissue. The mechanisms of development of these mobile encapsulated bodies in cows is unknown and it is not clear how, in the absence of a blood supply, there can be inflammatory cell infiltration, calcification and proliferation of fibroblasts.