NATURE AND SIGNIFICANCE OF EPICARDIAL LYMPHOID INFILTRATES IN CARDIACALLOGRAFTS

Background: Myocardial lymphocytic infiltration after transplantation is usually a manifestation of acute cellular rejection. However, purel y endocardial infiltrates are generally not regarded as rejection (so- called ''Quilty lesions''). The nature of epicardial lymphoid infiltra tion in cardiac allografts and its significance when observed in endom yocardial biopsies or autopsies are uncertain. Methods: Twenty-seven c ases of transplant-associated epicardial lymphoid infiltration were id entified; 16 cases were identified from 1602 consecutive transplant bi opsy specimens from 125 patients, and 11 from 14 autopsies, ranging fr om 1 to 35 months (mean 7.8 months) after transplantation. Results: Th e infiltrates were composed of aggregates of lymphocytes and histiocyt es distributed throughout the epicardium. Plasma cells were found in 5 2% of cases, with occasional eosinophils and rare neutrophils. Most we re vascular, and four autopsy cases had follicle formation. Twenty-fou r cases (93%) showed a mixed population of cells in a random distribut ion consisting of T cells in association with fewer B cells and histio cytes. Fifteen cases (nine autopsies, six biopsies) had acute rejectio n, and nine autopsies had chronic vascular rejection. Fourteen of twen ty-four cases (58%) showed concurrent Quilty lesion (nine autopsies, f ive biopsies), and the remainder showed at least one Quilty lesion in an earlier biopsy. Conclusion: Epicardial lymphoid infiltrates occur w ith significant frequency after heart transplantation and can be assoc iated with, and mimic, acute cellular rejection. However, they exhibit morphologic and immunophenotypic features which are distinguishable f rom rejection-associated infiltrates.