Lung transplant pathology. A comparative study of pulmonary acute rejection and cytomegaloviral infection

This article describes a comparative study performed to determine the histologic features of pulmonary rejection and cytomegaloviral (CMV) infection following lung transplantation. Rejection was defined clinically by findings of new pulmonary symptoms or radiographic changes or decreased oxygenation in the absence of documented infection in patients who were treated for rejection and improved. These patients also had negative CMV cultures. CMV infection was studied in a group of non-lung and non-bone marrow transplant patients and was defined by the presence of characteristic nuclear inclusions in lung biopsies. Ten rejection biopsies and nine CMV biopsies were examined. No histologic feature was unique to rejection, however; perivascular lymphocytic infiltrates occurred more frequently and more intensely in rejection than in CMV infection (p = 0.0029). Endothelialitis also occurred more frequently in rejection (p = 0.0331), but it was always seen in association with perivascular lymphocytic inflammation. In rejection, the inflammatory infiltrate was primarily perivascular, with extension into the interstitium in several cases. In contrast, CMV infection was characterized predominantly by interstitial inflammation with involvement of associated vessels. We conclude that although overlapping features are present in both processes, pulmonary rejection can be distinguished from CMV infection on the basis of histology.