Hi there, a (basic question ;-) )

While analyzing DEGs of metastatic samples, I got a question about the nature of metastatic tissue samples, which are being used for RNA isolation.

For example I got a gene expression file from breast cancer, which has metastasized liver. my question is whether such gene expression profile would belong to the metastasizing cells(e.g. breast here) or can it actually be a mix of metastasizing cells and the target cells(liver here)?

Thanks in advance,

Fahimeh