In view of the fact that elimination of caveolin-1 expression per se does not increase the spontaneous incidence rate of tumour formation in vivo in knockout mice, but rather promotes susceptibility to tumour formation in response to additional insult(s), it may be more appropriate to consider caveolin-1 as a ‘tumour susceptibility’ rather than a tumour suppressor gene. This evidence concerns the gene CAV1 and neoplasm.