Intrasarcolemmal proliferation of the VX2 carcinoma.

The VX2 carcinoma has been used extensively as an experimental model for different aspects of tumour behaviour and is usually maintained by serial intramuscular injections of tumour cells. The tumour grows rapidly, infiltrating between muscle bundles into the fibrous tissue replacing ischaemic muscle and into the vascular tree. The most interesting method of spread occurs within the sarcolemma and this may be responsible for the rounded cell nests described in this tumour.