parosteal osteosarcoma
Last reviewed 01/2018
A parosteal osteosarcoma is a low grade sarcoma which arises from the osteoblastic layer of the periosteum. It usually develops at the distal femoral or proximal tibial metaphysis in young adults.
Radiology reveals a dense bony mass on the bone surface but the cortex is not eroded and a linear gap is visible between the cortex and tumour.
It is treated by wide excision or if the site is inaccessible, by radiotherapy. The prognosis is better than with the "conventional" osteosarcoma, approaching a 90% cure rate.