Distinction of follicular hyperplasia from follicular lymphoma in B5-fixed tissues: comparison of MT2 and bcl-2 antibodies.

The distinction between follicular hyperplasia (FH) and follicular lymphoma (FL) is one of the classic problems in diagnostic hematopathology. Both MT2 and bcl-2 antibodies have been reported to be useful in making this distinction. To compare the utility of these two commercially obtained antibodies in paraffin-embedded sections, B5-fixed sections from 21 cases of follicular hyperplasia and from 46 follicular lymphomas were immunostained and the follicles evaluated. Neither MT2 nor the bcl-2 antibody showed definite follicular positivity in FH. In contrast, 66% of FLs were MT2 positive and 89% were bcl-2 positive (P < .02). MT2 staining was equivocal in 30% of FHs and 7% of FLs, whereas bcl-2 staining was equivocal in only one FL. In addition, MT2 staining was unsatisfactory in three cases. CD10 was negative (0% to 3%) in the three bcl-2-negative FLs tested and positive (> 10%) in 26 of 38 bcl-2-positive cases. These results demonstrate the utility of the commercially obtained bcl-2 antibody in distinguishing FL from FH in B5-fixed, paraffin-embedded tissue sections. They also illustrate the superiority of the bcl-2 antibody over MT2, which was less sensitive and more problematic to interpret.