Pediatric-Type Follicular Lymphoma Occurs in Both Children and Adults and Is Characterized by a High Proliferation Index and the Absence of a BCL2 Gene Rearrangement
Abner Louissaint, Adam Ackerman, Judith A Ferry, A John Iafrate, Lawrence R Zukerberg, Nancy L Harris, Robert P Hasserjian. Massachusetts General Hospital, Boston, MA
Background: Despite its excellent prognosis, pediatric-type follicular lymphoma (PFL) remains challenging to define; it is uncertain if this indolent lymphoma is merely defined by age or may also occur in adult patients. In an effort to better define the morphologic, immunophenotypic, and genetic characteristics of PFL, we performed a comprehensive retrospective analysis of clonal B-cell proliferations with follicular pattern (CFPs) occurring in patients <40 years of age.
Design: We reviewed 42 cases of CFPs, in patients ranging from 8 to 38y of age (median 17y, 35M/7F). 36 were Stage 1, and 6 were Stage 3 or 4. We evaluated histologic and immunohistochemical features (including Ki67 proliferation index, PI) as well as FISH and/or molecular genetic analysis for BCL2, BCL6, MYC, and MUM1 rearrangements. We then used parameters associated with Stage 1 disease to interrogate an independent group of 60 similarly characterized FLs occurring in patients ≥ 18 y of age.
Results: None of the 36 stage 1 CFP cases had progressive/recurrent disease; 5/6 of the stage 3 or 4 cases had progressive/recurrent disease, all of whom were treated with chemotherapy.
|Stage 1 (n=36)||Stage 3-4 (n=6)||P-value|
|LN size (median)||2.2 cm||2.3 cm||NS|
|BCL2 protein expression||4/33||5/5||p=0.0003|
|PI >40% (Ki-67)||28/28||0/4||p=0.0005|
|Complete Architectural effacement||7/30||4/5||p=0.03|
|Follicles > 2mm||27/34||0/5||p=0.001|