OBJECTIVETo study the possible loss of pan-T cell antigens CD2, CD3, CD5 and CD7 in Kikuchi's disease and to evaluate the role of T cell antigen loss in distinguishing benign from malignant T-cell lymphoid lesions.

METHODSFormalin-fixed and paraffin-embedded tissues of 33 cases of Kikuchi's disease and 15 cases of reactive lymphoid hyperplasia were studied by EliVision immunohistochemical staining for CD2, CD3, CD5 and CD7.

RESULTSTwenty-four of the 33 (72.7%) cases of Kikuchi's disease lost one or more of the pan-T cell antigens, including the loss of CD5 only (13 cases), CD7 only (1 case), CD2 only (1 case), CD2 and CD7 (2 cases), CD5 and CD7 (4 cases), CD2 and CD5 (2 cases), and CD2, CD7 and CD5 (1 case). Amongst these cases, the commonest antigen loss was CD5 (20 cases, 60.6%), followed by CD7 (8 cases, 24.2%) and CD2 (6 cases, 18.2%). Compared with the xanthomatous subtype of Kikuchi's disease, the loss of antigens was more commonly seen in the proliferative and necrotizing subtypes. Analysis of follow-up data showed that the loss of antigens in Kikuchi's disease was not significantly associated with the prognosis. In reactive lymphoid hyperplasia, the expression of CD2, CD3, CD5 and CD7 was seen in all cases with similar intensity, with no obvious pan-T cell antigen loss.

CONCLUSIONLoss of one or more pan-T cell antigens in Kikuchi's disease is demonstrated in present study, suggesting that the immunophenotypic pattern is not unique in T cell lymphoma.