Musculoskeletal Lymphoma: Imaging Features, Diagnosis, and Assessment of Treatment Response.

Lymphoma, a diverse group of neoplasms, has been frequently refined in classification, with over 100 types identified by the World Health Organization in 2022. Lymphoma represents 5% of new malignancies in the United States, the risk factors of which include genetic predisposition, infections, and inflammatory conditions. Extranodal lymphoma, constituting 25%-40% of cases, uncommonly involves the musculoskeletal system, with diffuse large B-cell lymphoma being the primary type. Bone lymphoma, classified as primary, primary multifocal, or secondary, predominantly affects the appendicular skeleton. Radiography and CT aid osseous evaluation and may reveal a lytic, sclerotic, mixed lytic and sclerotic, or near-normal appearance. MRI excels in soft-tissue and bone marrow assessment, and PET/CT plays a pivotal role in staging. Soft-tissue lymphoma, which involves various compartments, is best characterized with MRI, whereas US may be the modality first used for evaluation. Staging involves fluorodeoxyglucose (FDG) PET/CT, and treatment response is assessed through various imaging modalities. Skin involvement, commonly associated with primary cutaneous T-cell lymphoma, is described through stages, with FDG PET aiding diagnosis. Transspatial lymphoma involves multiple contiguous spaces and is known in the head and neck but not well documented in the musculoskeletal system. The authors provide comprehensive insight into musculoskeletal lymphoma by highlighting imaging findings crucial for diagnosis, classification, staging, and assessment of treatment response. ©RSNA, 2025.