A Clinicopathologic Evaluation of Follicular Lymphoma Grade 3A Versus Grade 3B Reveals No Survival Differences

Archives of Pathology & Laboratory Medicine, Aug 2004 by Hsi, Eric D, Mirza, Imran, Lozanski, Gerard, Hill, John, Et al

COMMENT

Follicular lymphoma is one of the most common types of non-Hodgkin lymphomas, comprising 22% of all non-Hodgkin lymphomas in a recent survey of more than 1400 lymphomas." A lymphoma primarily occurring in adults, FL is considered a clinically indolent lymphoma with a prolonged clinical course and with multiple relapses and recurrences. Cytologie grading of FL has long been suggested to be an important prognostic factor and has been a characteristic feature of many lymphoma classification systems over the years.5,10-13 The IWF demonstrated successively shorter survival in patients with FL stratified into 3 groups, based on the proportion of small cleaved and large cells.5 Although considered a single entity, the Revised European-American Classification of Lymphoid Neoplasms recommended a similar 3-tiered grading system6 .6 6 Notably, not all recent series have demonstrated survival differences between cytologie grades.14,15 The WHO classification recommends a similar cytologie breakdown, but also proposes subtyping grade 3 FL into A and B types, with the latter composed of sheets of centroblasts for investigative purposes.8 We retrospectively reviewed our experience with FL grade 3 to determine whether any differences in survival could be discerned that would support this practice.

Grade 3 FLs make up only a minority of all FLs. In 2 recent large series, grade 3 FLs represented 17.8% and 28.9% of FLs.9,15 This represents a relatively higher proportion than some older series (11.2% for the IWF, group D), perhaps due to different criteria for cytologie stratification.5 There are few data regarding the proportion of FL grade 3A in relation to grade 3B. In our series, which excluded diffuse large B-cell lymphomas (DLBCLs) with FL grade 3, 22% of cases of grade 3 FLs were grade 3B. Thus, FL grade 3B is an uncommon subtype of FL, perhaps representing roughly 5% of FLs. Ott and colleagues6 16 6 reported a series of FL that, when excluding DLBCL with grade 3 FL, contained 19% (15/77) FL grade 3. Of these 15 grade 3 FLs, 4 (26.7%) were FL grade 3B, a proportion quite similar to the current series.

The clinical features of our cohort of patients with grade 3 FL do not seem to differ substantially from those of even older published series of FL. However, there may be small differences, particularly with age of the patients. Looking at the IWF data for group D (follicular large cell), we see that our median patient age of 67 years is slightly older than the 55 years of the IWF series.5 Our male-female ratio was lower (0.9 vs 1.8), and the median survival was similar (3.7 years in our series vs 3.0 years). Most (86%) of our patients had high-stage disease (stage III or IV), again similar to the IWF data (73%).s These data are also similar to a more recent series. Rodriguez and colleagues17 reported a series of 62 patients with follicular large cell lymphoma with a slightly older median age of 57 years (male-female ratio, 1.1) and a longer median overall survival of 5.1 years; 76% were high stage.