[Differential diagnoses of malignant bone marrow diseases]

Bone marrow abnormalities are frequent radiological findings with a broad spectrum ranging from physiological conversion/reconversion to malignant infiltration.

This article summarizes important differential diagnoses of malignant bone marrow lesions and presents a practical diagnostic approach.

Narrative review based on the current literature, focusing on magnetic resonance imaging (MRI), computed tomography (CT) and supplementary techniques, such as chemical-shift imaging (CSI), Dixon sequences, diffusion-weighted imaging (DWI) and positron emission tomography CT (PET/CT).

Non-fat-suppressed T1-weighted MRI is central for bone marrow assessment. A signal intensity lower than skeletal muscle or intervertebral discs argues against simple reconversion and should raise the suspicion of infiltration. The CSI and Dixon techniques help differentiate benign mimics by demonstrating intralesional fat. Important differential diagnoses include metastases, leukemia, lymphomas, myeloproliferative disorders, multiple myeloma, reconversion, bone infarcts, chronic nonbacterial osteitis (CNO)/chronic recurrent multifocal osteomyelitis (CRMO), Langerhans-cell histiocytosis (LCH), enostosis and osteomyelitis.

The diagnosis requires integration of imaging patterns, fat content, mineralization, age, clinical context, tumor history and course. In unclear or aggressive findings, imaging follow-up or biopsy is required.