An American tourist goes on a trip to China.
While there, he is sexually promiscuous and doesn't use a condom.
A week after arriving home, he finds his penis is covered with bright green spots. Horrified, he goes to see his doctor.
Days later the doctor calls and says, "I've got bad news. You've contracted Mongolian VD. It's very rare. We know little about it. We have to amputate your penis."
The next day, the man seeks out a Chinese doctor, figuring he'll know more about the disease.
The Chinese doctor examines him and proclaims, "Ah, yes, Mongolian VD."
"What can you do?" asks the man. "My American doctor wants to amputate!"
The Chinese doctor shakes his head and laughs, "Stupid American doctors always want to operate. Make more money that way. No need to operate!"
"Oh, thank God!" the man replies.
"Yes!" says the Chinese doctor. "You no worry! Wait two weeks. Dick fall off by itself!"