Diffuse large B-cell lymphoma: morphologic and immunohistochemical analysis of bone marrow for staging, with emphasis on lymphoid aggregates.

Diffuse large B-Cell lymphoma (DLBCL) may infiltrate bone marrow (BM) and evaluation of BM plays an important role in DLBCL staging. This study used BM samples from DLBCL patients for staging and analyzed the use of immunohistochemistry in the diagnostic management of these cases by the pathologist. Patients with DLBCL submitted to BM biopsy/aspiration for staging were studied according to clinical aspects, morphologic aspects, and expression of CD20 and CD3. The characteristics of lymphoid aggregates in the bone marrow and the power of histopathological diagnosis were studied, with immunohistochemistry as the gold standard for the decision of a neoplastic infiltration definition. An isolated morphological analysis showed low sensitivity (42.9%) for lymphoma detection in BM, which is disadvantageous. The median of three lymphoid aggregates in the BM (p-value = 0.02) and the presence of increased reticulin fibers (grade 2) in the lymphoid aggregate (p-value = 0.01) had significant associations with neoplastic infiltration. A morphological analysis must be accompanied by an immunohistochemical analysis in all cases, or when this is not possible, in cases with two or more lymphoid aggregates or an increase of reticulin within them.