People who work in the medical profession see some pretty disgusting things. You'd be surprised what you can get used to over time though. A seasoned medical practitioner can often be pretty hard to unnerve with unpleasant sights and smells. Still, some medical fields have a higher turnover than others.
Take the doctors who deal with cancer. It can be pretty grueling, day in day out dealing with such desperately hopeful people. Seeing the toll that chemotherapy takes on people and the look on their faces when you have to tell them that it's returned.
As well as that there is something unnerving about the idea of a body literally turning on itself. Tumors are always pretty nasty at the best of times, but some are much more difficult to look at than others.
You ever hear the one about the lady with cancer in her uterus? The story usually goes that they take the tumor out but refuse to let her see it. She just has to know why though, so she sneaks a look or maybe the husband does. It varies, as does the description but usually the tumor is in its little specimen jar and its a horrible mess of human skin and teeth and hair.
That's called a Teratoma. They exist. It's not really something you want to show a fragile patient. Teratomas have been reported to contain hair, teeth, bone and even more complex organs such as eyes and hands, feet or other limbs. Usually, they form in the Testes or Ovaries but are also found inside the skull, in the brain, under the tongue or in any number of other structures along the midline of the body.
Fetiform Teratoma are rare forms that include one or more components resembling a malformed fetus. Forms that actually start to resemble a fetus are usually chalked up to parasitic twinning, but it's often less clear-cut with the less recognizable Teratoma. It's no secret that such tumors have been found with partial cranial structures, long bones and even rudimentary beating hearts.
Now, the question at this point might be, are you at risk of having one of these things start growing in your nuts? Probably not. That is to say, they say that these tumors are congenital, initially forming in your body even before you are born. If your doctor finds a Teratoma inside you then you have been carrying it around with you your entire life. They can however, begin growing and developing further later in life. Even if you have them removed there is no guarantee that it won't simply regrow.
The doctors who deal with these Tumors regularly usually only work in that particular field for a relatively short period of time. Invariably, they seem to find other disciplines to try their hand at or are promoted past the point where they need to operate themselves. Some few take to the bottle or quit altogether. If you are lucky and you find such a person you might be able to get them to talk about the things they found growing inside people's bodies. If you're lucky they may even tell the unsanitized version of the story.
And sometimes if you get them drunk enough, they might even tell you about the Teratoma that survive being removed from their host or where they are taken afterwards. If you push them, they may even be rash enough to take a guess at what they think actually causes them but always in hushed tones and wary eyes.
Perhaps you might even learn what they need them for.
But I wouldn't advise that you do.