{Reference Type}: Case Reports {Title}: Multifocal osteoclast-rich tumour in Paget bone disease and conventional giant cell tumour, two genetically distinct entities? Sequencing from a single case. {Author}: Haefliger S;Bubbear J;Davies C;Cottone L;Amary F;Tirabosco R;Cortes-Ciriano I;O'Donnell P;Flanagan AM; {Journal}: Skeletal Radiol {Volume}: 53 {Issue}: 1 {Year}: 2024 Jan 13 {Factor}: 2.128 {DOI}: 10.1007/s00256-023-04369-6 {Abstract}: Paget disease of bone is a metabolic disorder with a strong genetic component, characterised by pronounced disorganised bone remodelling. Complications of this disease include an increased risk of developing bone neoplasms. Here, we describe the case of a 60-year-old Italian patient with Paget disease of bone, presenting with an osteoclast-rich tumour. Our analysis of this entity, based on the clinical, morphological and genetic data (whole exome sequencing), suggests that osteoclast-rich lesions in Paget disease of bone are genetically distinct from classical giant cell tumour of bone. We discuss the importance of differentiating these osteoclast-rich lesions.