Fat necrosis in surveillance biopsies of heart transplants

Fat necrosis was observed in surveillance biopsies of five patients following heart transplant. This reaction is poorly documented in the literature, but in personal communication, some pathologists working in the field have had experience with it. Four of the cases developed two to six days after transplantation, but in the fifth case, fat necrosis developed ten months after transplantation. Autopsy study of one case showed extensive severe fat necrosis involving both donor and recipient tissues. The cause is not known, and the changes are independent of rejection. However, the fat necrosis can be found within the interstitial tissues of the myocardium and subendocardium and may be mistaken for rejection if lymphocytes and polymorphs are part of the inflammatory response. The only clinical finding thought to be related to the fat necrosis was the development of transient complete heart block in a patient in whom the International Society for Heart and Lung Transplantation (ISHLT) standardised rejection grading was never greater than IA.