title: Low histologic grade follicular lymphoma with high proliferation index: morphologic and clinical features.
abstract: Histologic grading has been used as a guide for clinical management in follicular lymphoma (FL). Proliferation index (PI) of FL generally correlates with tumor grade; however, in cases of discordance, it is not clear whether histologic grade or PI correlates with clinical aggressiveness. To objectively evaluate these cases, we determined PI by Ki-67 immunostaining in 142 cases of FL (48 grade 1, 71 grade 2, and 23 grade 3). A total of 24 cases FL with low histologic grade but high PI (LG-HPI) were identified, a frequency of 18%. On histologic examination, LG-HPI FL often exhibited blastoid features. Patients with LG-HPI FL had inferior disease-specific survival but a higher 5-year disease-free rate than low-grade FL with concordantly low PI (LG-LPI). However, transformation to diffuse large B-cell lymphoma was uncommon in LG-HPI cases (1 of 19; 5%) as compared with LG-LPI cases (27 of 74; 36%). In conclusion, LG-HPI FL appears to be a subgroup of FL with clinical behavior more akin to grade 3 FL. We propose that these LG-HPI FL cases should be classified separately from cases of low histologic grade FL with concordantly low PI.
authors.affiliation: Department of Pathology, Division of Hematology/Oncology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.
authors.forename: Sa A
authors.initials: SA
authors.lastname: Wang
authors.forename: Lan
authors.initials: L
authors.lastname: Wang
authors.forename: Ephraim P
authors.initials: EP
authors.lastname: Hochberg
authors.forename: Alona
authors.initials: A
authors.lastname: Muzikansky
authors.forename: Nancy Lee
authors.initials: NL
authors.lastname: Harris
authors.forename: Robert P
authors.initials: RP
authors.lastname: Hasserjian
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D049109:Cell Proliferation; D018450:Disease Progression; D005260:Female; D006801:Humans; D019394:Ki-67 Antigen / Q000276:immunology*; D008224:Lymphoma, Follicular / Q000276:immunology* / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D009361:Neoplasm Invasiveness
chemical_list: D019394:Ki-67 Antigen