Bone marrow lymphoid aggregates in malignant lymphomas

To examine the usefulness of molecular analysis of IgH gene rearrangement in assessment of clonality in bone marrow biopsies with lymphoid aggregates (LA) and/or nodular lymphoid hyperplasia (NLH) in patients with different subtypes of malignant lymphomas.

Five hundred and twenty nine samples of bone marrow biopsies, taken in a staging procedure at the time of the initial presentation of illness, were processed routinely. Results were grouped in positive, negative, and cases with LA or NLH. In 43 samples with present LA/NLH, polymerase chain reaction (PCR) analysis of the CDR3 region of immunoglobulin heavy chain gene (IgH) for B-cell clonality was performed.

Bone marrow malignant lymphoma infiltrates were present in 33.8% of lymphoma cases. The incidence of LA/NLH in bone marrow was 8.1%. LA/NLH were more frequently found in patients with extranodal disease and aggressive subtypes of B cell non-Hodgkin lymphoma (B-NHL), but there was no significant difference among the incidence according to the biological behavior of malignant lymphoma (P=0.232). Results of IgH-CDR3 region PCR analysis showed a monoclonal pattern in 1 case of Hodgkin lymphoma and in 1 control case, an oligoclonal pattern in 2 cases of extra nodal B-NHL, whereas all other had polyclonal.

The results support our initial hypothesis that LA/NLH could be differentiated from malignant infiltrates in bone marrow staging procedure of malignant lymphoma by topographic pattern and histocytomorphology of LA/NLH. Surprisingly, our patients with aggressive B-NHL, nodal, as well as extranodal, had LA/NLH in bone marrow biopsies more often than patients with indolent B-NHL.