Intracortical osteosarcoma is the rarest variety of osteosarcoma and represents less than 1% of all osteosarcoma cases.
Like other subtypes of osteosarcomas it also typically presents in adolescents and young adults (with the mean age of 19 years). It has slight male predominance.
Intracortical osteosarcoma is a low grade tumour of cortical bones and it typically does not extend into medullary canal and surrounding soft tissue until late stage of the disease. Histologically characterazied as a sclerosing variant of the osteosarcoma contains osteoid matrix with few fibroblastic foci within and mild degree of cellular atypia.
Tibial diaphysis is the most common site of this tumour.
It typically presents as an oval intracortical geographic osteolytic lesion in the diaphysis with surrounding sclerosis and usually measures about 4 cm in length. Multiple calcific foci can be seen within the lytic region, suggesting osteoid matrix.
CT reaveals osteolytic lesion with surrounding sclerosis and rare matrix calcific specks.
It was believed that intracortical osteosarcoma was confined to the cortex of bone and does not show intramedullary or superficial involvement but it may involve medullary canal as well as surrounding soft tissue. It shows peripheral enhancement after intravenous contrast administration.
- T1 - hypointense
- T2 - intermediate to high signal intensity
- STIR - to detect perilesional edema and intramedullary extension of the tumour.
Treatment and prognosis
Although reported cases have shown slow progression and a low-grade histological appearance,recurrence and distant metastasis have also been reported. The ideal treatment is surgical resection with an adequate margin with adjuvant chemotherapy can be considered. With surgical resection and adjuvant chemotherapy overall prognosis is good.
Differential considerations on plain film include
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