Primary splenic large B-cell lymphoma
Primary splenic large B-cell lymphoma is an uncommon entity. The spleen is more commonly involved by splenic marginal zone lymphoma, mantle cell lymphoma, or follicular lymphoma (1). Most frequently splenic large B-cell lymphoma forms discrete masses, however other patterns may occur. The patterns are classified into 3 types based on the gross appearance, macronodular, micronodular, and diffuse. The macronodular pattern is characterized by macroscopic large, solitary or multiple nodules. The micronodular pattern is characterized by a miliary pattern of multiple white pulp micronodules that are visible grossly (as seen in this case). The diffuse pattern consists of grossly undetectable pattern, which reveals itself microscopically.
Mollejo et al reviewed the clinical and pathologic findings of thirty-three cases of splenic large B-cell lymphoma. The macronodular group showed overall favorable clinical course in comparison to the other groups. Immunophenotypically, the macronodular group demonstrated bcl-6 positivity and a subset expressed CD10 and bcl-2. The micronodular group clinically behaved worse than the macronodular group and often expressed bcl-6, similar to the macronodular and diffuse groups. The group with a diffuse pattern also had a poor prognosis and presented at a later clinical stage. The diffuse cases appear to originate in the red pulp. They had variable expression of IgD and p53.
The multitude of chromosome aberrations may suggest an advanced stage of disease and a poor prognosis. Interestingly, the cytogenetics studies demonstrated an 11:14 translocation by classic methods, which suggested the diagnosis of mantle cell lymphoma. However, fluorescent in-situ hybridization (FISH) studies showed an IgH rearrangement without the CCND1 rearrangement diagnostic of mantle cell lymphoma. This demonstrates the utility of using FISH studies to accurately characterize a translocation.
Primary splenic large B cell lymphomas are interesting, but uncommon neoplasm. Further characterizing these neoplasms will likely require large multicenter studies to examine larger numbers of cases, but may help to clarify their behavior and appropriate therapy.
Contributed by Matthew Smith, MD nd Fiona Craig, MD