Decreased CD10 expression in grade III and in interfollicular infiltrates of follicular lymphomas

CD10 expression in various grades and interfollicular infiltrates of follic ular lymphoma (FL) has not been well documented Immunohistochemical stainin g for CD10 (clone 56C6) was performed on paraffin-embedded tissue from 26 c ases of classic FL. Negative or weak expression of CD10 was more frequent i n grade III (5/6 (83%]) than in grade I FLs (3/15 [20%]). CD10+ interfollic ular infiltrates were present in 16 cases. Sh (38%) of 16 cases showed that CD10 expression was strong or moderate in follicular areas but weak or neg ative in interfollicular infiltrates. Our results suggest that CD10 express ion is frequently weak to negative in grade III and in interfollicular infi ltrates of FLs. Therefore, lack of CD10 expression on small specimens, such as from needle core biopsy or fine-needle aspiration, does not preclude th e possibility of a diagnosis of FL. Furthermore, lack of CD10 expression in diffuse large B-cell lymphoma does not exclude the possibility that the ne oplastic lymphocytes are of follicle center cell origin.