parosteal osteosarcoma
Pronunciation: pair-AH-stee-al
A low-grade surface osteosarcoma arising from the outer layer of cortical bone, typically around the knee.
Full Definition
Parosteal osteosarcoma is a rare variant of osteosarcoma that arises from the parosteal tissues on the surface of bone, most commonly affecting the posterior distal femur. Unlike conventional high-grade osteosarcoma, parosteal osteosarcoma is typically low-grade with a more indolent course and better prognosis. It presents as a lobulated, mineralized mass attached to the bone surface with a characteristic 'cauliflower' appearance on imaging. The tumor tends to wrap around the bone circumferentially and may eventually involve the medullary canal in advanced cases.
Usage
Usage note: Distinguished from periosteal osteosarcoma by location and grade; parosteal is low-grade surface tumor.
In Context
- "The lobulated calcified mass on the posterior distal femur was consistent with parosteal osteosarcoma." — Imaging interpretation
- "Histopathology confirmed low-grade parosteal osteosarcoma without high-grade transformation." — Pathology report