The incidence and mechanism of transphyseal spread of osteosarcoma of long bones.

Although the physeal cartilage is considered resistant to invasion by metaphyseal osteosarcoma, no objective clinical proof exists to support this view. Fourteen cases of osteosarcoma of long bones in patients ranging in age from ten to 19 years with open physes were reviewed to determine the incidence of transphyseal spread. The physeal cartilage was not crossed in only two cases. In the remaining 12 cases the tumor crossed the cartilaginous plate partially or completely, remaining in the epiphysis in seven and crossing the articular cartilage and involving the joint in five. Histologic sections showed that increased vascularity occurs initially, followed by osteoclastic and chondroclastic activity at the physeal plate with subsequent tumor tissue invasion. The incidence of transphyseal spread in the three published series (total of 64 cases, including the present 14 cases) is 81.2%. This is contrary to the often published unsupported statements of others. Transphyseal spread of osteosarcoma is the rule rather than the exception.