Q. Where do you get this done?

Demand it first from your doctor. Your doctor will then likely coordinate with the pathology department to get a tumor sample from you (i.e through previous biopsy or surgically removed sample that is sitting preserved in a lab), or possibly through new blood draw. The doctor will then have those samples send over to one of the places above. They will also work with your health insurance provider on coverage / reimbursement for the diagnostic test.