Morphologic criteria for the differentiation of follicular lymphoma from florid reactive follicular hyperplasia: a study of 80 cases.

A study was made of 80 patients whose lymph nodes were characterized by the presence of follicles throughout the lymph node. The patients were divided into two groups on the basis of the clinical follow-up information. The first group consisted of 20 patients who were alive and disease-free at the end of five years without therapy. The patients in this group were classified as having florid reactive follicular hyperplasia (FRFH). The second group of 60 patients had progressive, recurrent, clinically active disease and were classified as having follicular lymphoma (FL). Forty-six were dead of active disease, and 14 were alive with disease. Various morphologic parameters were evaluated at low and high magnification, and statistical comparisons were made between FRFH and FL. Although several criteria were helpful in distinguishing FRFH from FL, the single most valuable criterion was the type of pattern encountered. Follicles of variable size and shape lying adjacent to each other throughout the lymph node without or with very little intervening tissue are diagnostic of FL. This pattern was evident in 85% of the FL cases, but was not observed in any of the cases of FRFH.