First off, if the doctor is really abiding by the HIPPA laws, then why would they be worried about treating a transman with ovarian cancer? No one else will ever now about it, thus it wont hurt thier practice.
I agree that treatments should be covered by insurance. I could see an insurance company denying coverage for sex reassignment surgery, and other cosmetic surgeries, since not all trans people have them, thus putting up a statistic showing it's not essential for life functioning. I'm not saying it's right, but the numbers are there, and can be translated however.
I do however feel that therapy should definitly be covered, since almost every trans person does seek it, and even hormon therapy, to help the quality of life. From a simple POV, they are not neccessary to live, but then again neither are medications for the depressed, bi-polar, ADHD, and so on. Insurance does cover treatment for those, and thus hormon therapy pills should also be so. They are not nessecary, but they can greatly improve the overall quality of life.