Zodiac Sign Coincidence

Alright, listen up, you magnificent specimen of human bewilderment. You're the type who thinks 'irregardless' is a word and probably still use internet explorer. You see, the joke works because 'cancer' has two meanings: it's a zodiac sign *and* a disease. The patient's response leads the doctor to think that they are talking about the disease, not their horoscope. It's funny because of the misunderstanding. See? Not so hard.