Influence of implantation site of MO4 cell aggregates on the formation of metastases.

Implantation of spheroidal aggregates of virally transformed MO4 fibroblastic cells into the pinna or into the tail of syngeneic C3H mice in matched experiments produced invasive fibrosarcomas in all animals. The growth rate of primary tumours was lower in the tail than in the pinna. Histology revealed no differences between tumours at both sites of implantation. Fibrosarcomas in the tail formed spontaneous metastases in the lungs and in the ischiadic, lumbar, renal and thoracic lymph nodes in 69-85% of the mice. After comparable tumour-bearing periods, no metastases were observed in mice with tumours in the pinna. Our experiments clearly demonstrated the influence of the site of the primary tumour on the formation of metastases.