Here's a truly weird article, which a sticks in my mind a week after reading it:
"Clark had seen teratomas. They were common in the reproductive tract, often found accidentally in the course of an operation or on a scan done for some other reason.
These strange cysts have been a source of fascination since their discovery in the 19th century because, although smooth and normal-appearing on the outside, on the inside they often contain hair and teeth and other tissues not normally seen in the reproductive system.
The name “teratoma” is derived from the Greek word for “monster,” because of their creepy contents. These cysts rarely cause trouble and are usually removed only if they get too large or cause pain. This cyst was the size of a peach pit. Could a small growth do all this?" (from Brain Drain)