Metastasis spread from syngeneic murine tumours. Establishment of a test protocol for comparisons between ascites tumours and their progenitors.

We have transformed two new MC-induced tumours, a sarcoma (MCB31-SC), into ascites form. When transplanted s.c. these ascites tumours grow as solid, quite undifferentiated tumours, (AS = ascites solid tumours). We compared the metastasizibility of the AS tumours with that of the parent tumours. In doing so, we used both the tail and the hind leg as transplantation sites. The tumours can be radically removed from both sites by amputation, which prolongs the survival time of the animals and permits metastases to grow into detectable sizes. As registered grossly and by microscopy, the AS tumours have a greater tendency of spread than the parent (SS/SC) tumours. MCB-21 AS grows quicker than 21-SS and gives rise to more lymph node metastases. When transplanted to the tail the AS tumour also gives a higher incidence of lung metastases. We detected no such difference by leg-transplanted tumours. MCB31-SC did not produce any detectable metastases at all, while 31-AS, particularly from the tail, gave rise to numerous lymph node and lung metastases. There were no differences in tumour size or growth rate to account for this difference. Thus ascites conversion has changed the carcinoma MCB31-SC into an undifferentiated, metastasizing tumour, as detected by our procedure. The design of test protocols to detect metastasizibility is discussed.