Primary bone lymphoma is an uncommon malignancy that accounts for less than 5% of all primary bone tumors. The radiographic appearances of primary bone lymphoma are variable, and, because the lesion can appear near normal on plain radiographs, a second modality such as bone scintigraphy or magnetic resonance (MR) imaging should be used. Despite this variability, the presence of a solitary, permeative, metadiaphyseal lesion with a layered periosteal reaction on plain radiographs and a soft-tissue mass on MR images, especially in a patient older than 30 years, is highly suggestive of lymphoma. The case for a diagnosis of primary bone lymphoma is further strengthened if the soft-tissue mass and marrow changes are associated with surprisingly little cortical destruction. Primary bone lymphoma has a better prognosis than many other malignant bone tumors; therefore, early identification allows for appropriate treatment. MR imaging not only permits early identification but also depicts the extent of soft-tissue involvement and can be used to assess the outcome of treatment.
Primary bone diffuse large B-cell lymphomas (PB-DLBCL) are uncommon extranodal lymphomas. Herein, we report the clinical, pathologic, immunohistochemical, and molecular features of 21 cases of PB-DLBCL. The mean age of the patients was 54 years (range: 13 to 85 y). The male and female ratio was 1.6:1. The tumors consisted of diffuse sheets of large atypical cells or a polymorphous mixture of small-to-large cells with large multilobated nuclei, fine chromatin, and inconspicuous to prominent nucleoli. Twelve (57%) cases were non-germinal center B (GCB) and 9 (43%) were GCB subtype based on immunohistochemical classification. B-cell lymphomas (BCL)-2 was positive in 17/21 (81%), TP53 in 11/21 (52%) positive and the mean MIB-1 index was 57%. Polymerase chain reaction showed 10 cases with immunoglobulin heavy-chain (IGH) and 4 cases with IGH/BCL-2 gene rearrangement. The fluorescence in-situ hybridization analyses showed 14% of cases with BCL-6, 19% of cases with BCL-2, and 9% of cases with C-MYC gene rearrangement. Age <60 years and complete response to initial treatment were significant predictors of survival outcome (P< or =0.05). Even though no association was observed between the subtype of PB-DLBCL (GCB vs. non-GCB), BCL2, TP53, MIB1 index and overall survival (P>0.05), due to small sample size, and variability in treatment received, this analysis may be interpreted with caution.
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