My biopsy results came back to the doctor in 2-3 days. Yet, I waited to discuss them with the doctor and didn't call in for the results. In my case, that was much better since I was positive for cancer.
I have thought it would be great if they called immediately if the results were negative, but then I guess you'd know if they didn't call that something was up, and then you'd have to wait some days to talk to the doctor in a private discussion. So, I'm not sure which is worse.