Proliferation centers in bone marrows involved by chronic lymphocytic leukemia/small lymphocytic lymphoma: a clinicopathologic analysis

Objectives Proliferation centers (PCs) are a characteristic finding in chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) lymph nodes, and their presence and extent in this site are not currently felt to be related to clinical course. In contrast, detailed clinicopathologic analyses of bone marrow (BM) PCs have not been previously reported. Methods The PCs in 88 CLL/SLL BMs from 45 patients (pts) were graded (0-4) and were correlated with other morphologic, immunophenotypic, cytogenetic, and laboratory features. Results Proliferation centers were present in 69 BMs (78%) from 32 pts (71%) and were distinct/prominent (grades 2-4) in 21 pts (47%), with the latter more commonly found in follow-up BMs (1/7 diagnostic BMs vs 49/81 follow-up BMs; P = .04). When present, PCs were most commonly graded as distinct nodules easily visible on ×10. No relationships were identified between PCs and any complete blood count parameter, serum lactate dehydrogenase or IgG levels, degree or pattern of BM involvement, blood morphology, CD38 and FMC7 expression by flow cytometry, or fluorescence in situ hybridization results, when the first encountered BM was considered for each patient. Conclusions This represents the first detailed analysis of PCs in CLL/SLL BMs. In our tertiary center, PCs were seen frequently, in approximately three-fourths of cases. There were no statistical associations identified between PCs and cytogenetic, immunophenotypic, or other laboratory and morphologic findings.