Revisiting the WHO classification system of bone tumours: emphasis on advanced magnetic resonance imaging sequences. Part 2.

Similarly to soft tissue tumours, the World Health Organisation (WHO) classification categorises bone tumours based on their similarity to normal adult tissue. The most recent WHO classification provides an updated classification scheme that integrates the biological behaviour of bone tumours, particularly cartilage-forming tumours, and tumours are now further subdivided as benign, intermediate (locally aggressive or rarely metastasising), and malignant. Radiologists play an important role in the detection and initial characterisation of bone tumours, with careful analysis of their matrix mineralisation, location, and overall anatomic extent including extra-compartmental extension and neurovascular invasion. Radiography remains central to the detection and characterisation of bone tumours; however, magnetic resonance imaging (MRI) is the ideal modality for local staging. This review will discuss the most recent updates to the WHO classification of bone tumours that are relevant to radiologists in routine clinical practice. The utility of advanced MRI sequences such as diffusion-weighted imaging, dynamic contrast enhanced sequences, and magnetic resonance spectroscopy that may provide insight into the biological behaviour of various bone tumours is highlighted.