I've Had A Slowly Growing Mass On The Vas Deferens

I've had a slowly growing mass on the vas deferens for a while now (a lot of months or a few years). it doesn't hurt, isn't one solid mass and is about the size and shape of a marble cut in who but when squeezed even slightly easily gives way. Another thing is that my semen isn't white and gel-like but totally clear and slippery. I'm 16 at the moment, please help. Could it be cancer or something else?