Follicular lymphoma in staging bone marrow specimens: correlation of histologic findings with the results of flow cytometry immunophenotypic analysis.

CONTEXT Bone marrow (BM) examination is part of the staging workup of lymphoma patients. Few studies have compared BM histologic findings with results of flow cytometric immunophenotyping analysis in follicular lymphoma (FL) patients. OBJECTIVE To correlate histologic findings with immunophenotypic data in staging BM biopsy and aspiration specimens of FL patients. DESIGN Bone marrow biopsy specimens of untreated FL patients were reviewed. Histologic findings were correlated with 3-color flow cytometric immunophenotyping results on corresponding BM aspirates. RESULTS Bone marrow biopsy specimens (with or without aspirates) of 114 patients with histologic evidence of FL in BM were reviewed. There were 76 bilateral and 38 unilateral biopsies performed, resulting in 190 specimens: 187 involved by FL and 3 negative (in patients with a positive contralateral specimen). The extent of BM involvement was < 5% in 32 (17.1%), > or = 5% and < or = 25% in 102 (54.6%), > 25% and < or = 50% in 27 (14.4%), and > 50% in 26 (13.9%) specimens. The pattern of involvement was purely paratrabecular in 81 (43.3%), mixed in 80 (42.8%), and purely nonparatrabecular in 26 (13.9%). Immunophenotyping was only performed unilaterally, on BM aspirates of 92 patients, and was positive for a monoclonal B-cell population in 53 (57.6%) patients. Immunophenotyping was more often negative when biopsy specimens showed FL with a purely paratrabecular pattern. For comparison, we assessed 163 FL patients without histologic evidence of FL in BM also analyzed by flow cytometric immunophenotyping. A monoclonal B-cell population was identified in 5 patients (3%). CONCLUSIONS Our data suggest that 3-color flow cytometric immunophenotyping adds little information to the evaluation of staging BM specimens of FL patients.