Sr90-Induced Osteosarcomas

Abstract

Sr90 (NO3)2 was given as a single intraperitoneal dose to 200 male CBA mice. The dose corresponded to 0.67 µC/g. body weight. Osteosarcomas developed in 90 per cent of the mice and lymphatic leukaemia in about 5 per cent. The first and the last of the osteosarcomas were detected 181 and 462 days respectively after the injection of Sr90. The bone tumours were generally multiple with a mean of 2.2 tumours per mouse and in 10 per cent of the animals 4 or more tumours developed. About 90 per cent of the tumours originated in the parts of the skeleton posterior to the 13th thoracic vertebra. Most of the tumours originated in the long bones, particularly the femur and the tibia, followed by the vertebrae, especially the 6th lumbar and first sacral vertebrae. Metastases, particularly in the lungs and liver, were observed in a few mice; all these originated from boneforming tumours and were themselves boneforming. The skeletal tumours can be divided into 2 histological types. I. Predominantly non-boneforming, fibroblastic osteosarcoma. II. Predominantly boneforming, osteoblastic osteosarcoma. The majority (83 per cent) were of the osteoblastic type. Both types of tumour could occur in one animal and even within one bone. An argyrophilic stroma was formed in inverse ratio to the amount of bone formed. The number of mitoses was significantly higher in the fibroblastic than in the osteoblastic tumours; the fibroblastic tumours grew much more rapidly. Serum alkaline phosphatase activity was highly significantly increased for mice with osteoblastic tumours and highly significantly decreased for mice bearing fibroblastic tumours. Both types of tumour could be transplanted isologously.