Hi @LibbyA. If you are referring to genomic tests, they go by a range of names based on the brand. There are a number, applicable to different scenarios. Some doctors rate some of them higher than others. I had Endopredict, which was applicable to me because my tumour was under 2cms and there was no spread to the lymph nodes.
They test the slicecof your tumour that is kept in storage somewhere as is standard. I'm not sure how long they keep them for but at least five years I believe.
This link from the US breastcancer.org website provides an excellent explanation:
https://www.breastcancer.org/symptoms/diagnosis/genomic_assaysK xox