Which is more likely:
1.An oncology surgeon who does transplants?
2.A transplant surgeon with mostly cancer patients?
It is a pretty odd question. I doubt that either of them are common at all but #2 is more plausible to me.
I’m an odd duck Shag. 
I agree with Shag, on both points.
A transplant surgeon could end up doing a lot of livers on folks with hepatomas.
Less likely to do many transplants on renal cancer patients, though. Usually only one kidney involved in the cancer, after all.
Though a surgical oncologist would also have similar opportunities, I suppose.
My inclination was #2 as well, thanks guys.
It’s definitely 3. A medical oncologist who does stem cell transplants.
Now a psychiatrist who does optical exams - those are hard to find.