<prompt> Which of the following is bone forming malignant tumour?Osteoid osteomaOsteosarcomaChondrosarcomaGiant cell tumour  <response>: Ans. is b i.e., Osteosarcoma o Bone-forming tumours are a sub-set of bone tumours that are characterised by their propensity to form excess osteoid. They can be further subdivided into benign and malignant tumours.Benign tumours Osteoid osteoma Osteoblastoma Bone island enostosis Osteopoikilosis OsteomaMalignant tumourso Malignant bone-forming tumours are all osteosarcomas. Osteosarcoma conventional Telangiectatic osteosarcoma Low-grade central osteosarcoma 