CD30 ANTIGEN EXPRESSION IN FLORID IMMUNOBLASTIC PROLIFERATIONS - A CLINICOPATHOLOGICAL STUDY OF 14 CASES

Reactive immunoblastic proliferations may be confused with certain typ es of non-Hodgkin's lymphoma and Hodgkin's disease on morphologic grou nds. In addition, a characteristic antigen, CD30 (Ki-1; BerH2) on thes e neoplastic entities may be observed in morphologically atypical yet reactive florid immunoblastic proliferations such as those associated with acute infectious mononucleosis. Although it has been documented, a large series determining the frequency and extent of CD30 antigen ex pression on a variety of nonneoplastic immunoblastic proliferations is lacking. The authors studied 14 florid immunoblastic proliferations ( 9 in lymph nodes and 5 in tonsils) for CD30 antigen expression and for B- and T-cell paraffin markers. In situ hybridization to determine th e presence of Epstein-Barr virus (EBV) genomes also was performed. Cas es were classified into monospot-positive acute infectious mononucleos is (4 cases), EBV-related lymphoproliferative disorder suggestive of a cute infectious mononucleosis (5 cases), and other etiologies (5 cases ). CD30 Antigen expression was found on the immunoblasts in cases from all three categories and overall in 9 (64%) of 14 specimens. CD30 rea ctivity in the positive cases varied from occasional to numerous posit ive cells; 4 samples (3 EBV-related lymphoid proliferations and 1 vacc ine-related lymphadenopathy) had numerous CD30-reactive immunoblasts. Expression of CD30 antil:en on B or T cells and prominence of B or T c ells within a proliferation were variable. Significant ''atypia'' of i mmunoblasts was found only in EBV-related disorders and correlated wit h B-cell prominence of the infiltrate. Appropriate clinical correlatio n and ancillary laboratory data are necessary to assist in differentia ting these CD30+-reactive disorders from similar-appearing malignant l ymphomas. Most important, a fresh tissue sample should be procured and adequately processed to allow for comprehensive determination of clon ality and cellular lineage.