The colony forming efficiency of single cells and cell aggregates from a spontaneous mouse mammary tumour using the lung colony assay.

Single cell suspensions of spontaneous C3H mammary tumours did not produce colonies in the lungs of syngeneic mice after intravenous injection whereas cell aggregates obtained from similar tumours did. The number of colonies formed after the injection of aggregates was related to aggregate size and was proportional to the number injected.Single cells grew in an intramuscular site and in vitro and it was also found that if spontaneous tumours were passaged in vivo a few times single cells would grow in the lung.