[1516] Follicular Lymphoma (FL) like B-Cells of Uncertain Significance (In Situ FL) Has a Low Rate of Progression, but Is Very Frequently Present in Biopsies Preceding Overt FL and a Moderate Proportion Is Associated with Other Lymphoid Neoplasms

Raju K Pillai, Steven H Swerdlow. University of Pittsburgh School of Medicine, Pittsburgh, PA

Background: It has been proposed that in situ FL be called FL like B-cells of uncertain significance (FLBUS) because of growing concern that it is not an overt lymphoma. However, variable proportions of coexistent or subsequent FL and other lymphomas (ML) have been reported in a limited number of studies. Parameters predictive of progression are not established. In addition, the proportion of overt FL preceded by FLBUS is unknown.
Design: 26 biopsies with FLBUS were reviewed including assessment of BCL2+ follicles, associated ML & clinical followup. In addition, prior “benign” lymph node (LN) biopsies from 6 patients who developed overt FL were retrieved & stained for BCL2, CD10, CD20 & CD3.
Results: 11/26 (42%) patients with FLBUS had concurrent ML–FL-2, DLBCL-2, CLL/SLL-2, MALT-1, in situ mantle cell ML (MCL)-1, periph T-cell ML (PTCL)-2 & classical HL-1. 2/26 (8%) had subsequent ML (FL with prior PTCL, DLBCL) at 0.5-1 mo. 14/26 (54%) did not develop any ML (median followup 27 (1-68) mo.). Most cases had a high proportion of BCL2+ follicles with most of these having >25% BCL2+ cells.

Clinicopathologic Features, median (range)

	All_cases*	Concurrent FL/DLBCL	Subsequent FL/DLBCL	Concurrent other B_cell_ML	No Lymphoma
Cases, #	26	4	2	4	14
Age, yr	75(30-87)	66(30-81)	75(71-78)	80(74-87)	69(40-86)
M:F	18:8	2:2	1:1	3:1	11:3
BCL2+ Foll, Abs #	11(1-207)	20(3-31)	14(10-17)	7(1-11)	11(4-207)
BCL2+ Foll, %	79(2-100)	72(5-97)	88(85-91)	44(2-75)	88(6-100)
% of BCL2+ Foll with <25% BCL2+ cells	27(0-86)	37(0-43)	26(10-41)	39(0-86)	21(0-73)
% of BCL2+ Foll with >50% BCL2+ cells	43(0-100)	47(32-100)	61(53-70)°	15(0-45)°	50(5-100)
% of BCL2+ Foll with >95% BCL2+ cells	10(0-100)	10(10-33)	13(6-20)	0(0-14)	12(0-100)
Follow-up, mo	29(1-68)	37(12-58)	32(1-63)	37(2-66)	27(1-68)
Known Rx	8	3	1	1	2
Alive	22	4	1	2	13
Dead	4	0	1-DLBCL	2-CLL/SLL	1-No ML

*Includes 1 PTCL & 1 HL not in other columns;°p=0.03

No significant differences were identified for the various BCL2-related parameters between the major groups of patients with 1 exception. 8 patients were treated and 4 died. 5/6 (83%) "benign" LN biopsies obtained 1-108 mo. prior to diagnosis of an overt FL (median 56 mo.) had FLBUS.
Conclusions: Although isolated FLBUS appears to have a low rate of progression, most FL are preceded by FLBUS, analogous to the situation with CLL and MCL. In addition, almost half of the FLBUS had potentially related or often apparently unrelated lymphomas. The extent of FLBUS did not have significant implications.
Category: Hematopathology

Monday, March 19, 2012 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 216, Monday Morning