Cytomegalovirus-infected cells express Leu-M1 antigen. A potential source of diagnostic error

The authors examined cytomegalovirus (CMV)-infected tissues and Hodgkin's Disease (HD) cases with immunohistochemical assays for Leu-M1 and CMV. The cytologic characteristics were correlated with immunostaining patterns. Cytomegalovirus-infected cells in lymph node, lung, and esophagus sections showed Cowdry type A inclusions, and many had granular cytoplasmic inclusions. All infected cells showed nuclear staining with an anti-CMV antibody. Leu-M1 reacted with CMV-infected cells in cytoplasmic areas, particularly near the nucleus simulating the characteristic staining pattern of Reed-Sternberg (R-S) cells. Cytoplasmic staining intensified as the intranuclear inclusions increased in size. Reed-Sternberg cells showed characteristic Leu-M1 positivity along the cell membrane and golgi zone. At times, Leu-M1 staining of CMV-infected cells was indistinguishable from that of R-S cells. None of the R-S cells reacted with the antibody to CMV. Recognition of the reactivity of Leu-M1 with CMV-infected cells is important in avoiding misdiagnosis of CMV lymphadenitis as HD.