Please be careful when you word things. There are a great many things that it could be, and jumping to cancer or having a "tube" stuck up the vagina is a bit on the extreme.
Renee0411--- There is honestly a lot that could be going on. Have you always been overweight? Or did you put on a lot at once. Also. Are you on medication, do you exercise, have you had a change in sleep or diet? Brown discharge (and also black) is usually an indicate of old blood being expelled from the body. Since you've never had sex, pregnancy as well as STD can be ruled out. It could be due to ovulation, stress, irritation (if you insert anything into the vagina) cyst, etc. Your best chance would be to see a doctor. Usually it's nothing that is concerning, but a doctor could find out what it is and if it IS something serious early treatment is best.
u might have cancer or idk if u do u need suregery and if u dont need something like a tube up ur tweetie and go to the doctors !