Primary Lymphoma of Bone: Imaging Findings to Improve Diagnosis of a Rarely Considered Disease Prior to Biopsy

Objective: Primary lymphoma of bone (PLB) is a rare malignant bone tumor often presenting in the fifth-sixth decades involving appendicular long bones. Published radiological findings indicate that PLB typically presents as a moth-eaten osteolytic lesion with periosteal reaction, while MRI commonly demonstrates marrow infiltration with extraosseous extension. Given rarity and variable appearances, PLB may not be primarily considered prior to biopsy. Our objective was to evaluate preoperative imaging findings in effort to increase awareness and improve a perceived deficiency in preoperative diagnosis. Materials and Methods: Following IRB approval, retrospective review identified 60 patients with newly diagnosed bone lesions proven to represent PLB in accordance with WHO definition. Preoperative radiographs (n = 46), MRI (n = 33) and PET (n = 37) were independently reviewed by two radiologists. At radiography, lesions were classified: purely lytic, mixed, purely sclerotic, or occult; lytic lesions were graded utilizing Lodwick’s classification. At MRI, lesions were defined as focal or infiltrative and the presence or absence of extraosseous disease was recorded. Extraosseous masses were defined as small (<1 cm) or large (>1 cm) and subjectively correlated with degree of cortical destruction. At PET, lesions were recorded as FDG-avid or not. Primary radiograph reports when available (n = 33) were reviewed and exact wording of differential considerations was recorded. Results: Radiographs demonstrated mixed (n = 22), lytic (n = 15), and sclerotic (n = 8) appearances; one radiographically occult lesion was seen by MRI. Lytic lesions were graded: IB (n = 3), IC (n = 5), II (n = 4), and III (n = 3); none were IA. At MRI, 30 lesions were infiltrative and 3 were focal; 11 were not associated with extraosseous extension, while 22 showed bony disease with small (n = 7) or large (n = 15) soft tissue mass. Of large masses, 13 demonstrated minimal cortical destruction. At PET, 36 demonstrated FDG uptake; one study was technically limited. Review of reports found that only 5 included “lymphoma” as a Corresponding author. J. T. Caracciolo et al. 98 diagnostic consideration. Conclusion: Contrary to most published data, we suggest that PLB typically demonstrates some degree of osteosclerosis, often a mixed pattern of sclerosis and lucency; purely lytic lesions may be less common. Similar to existing reports, MRI commonly demonstrates marrow infiltration with extraosseous extension of disease, typically a large soft tissue mass with disproportionate (minimal) cortical destruction. Familiarity with these findings should improve preoperative consideration of PLB in the appropriate clinical scenario when a new osteoblastic lesion is identified.