Objective: To study the value of loss of CD10 expression in the diagnosis and differential diagnosis of follicular lymphoma (FL).
Methods: One hundred and twenty-six cases of FL and 31 cases of reactive follicular hyperplasia (RFH) were studied with routine microscopy and immunohistochemistry.
Results: Loss of CD10 expression was observed in 37 cases (29.4%) of FL. Three patterns of CD10 loss were demonstrated, as follows: diffuse CD10 loss in all of the neoplastic follicles (33/37, 89%), CD10 loss in most follicles (3/37, 8%) and CD10 loss in only a few follicles (1/37, 3%). In general, loss of CD10 was frequently seen in higher-grade FL. Morphologically, the cases with CD10 loss showed follicular architecture. The neoplastic follicles in high-grade FL were of various sizes and showed irregular margins, while those in low-grade FL were relatively uniform in size with regular margin. Sometimes, the CD10-negative FL cells contained a clear cytoplasm, mimicking monocytoid B cells. On the other hand, CD10 expression was found in all of the 31 cases of RFH studied, with the exception of occasional individual or regressed follicles.
Conclusions: The expression of CD10 differs in FL and RFH. Loss of CD10 expression is seen mainly in FL. It is thus considered as a valuable parameter in differentiating between FL and RFH.