Enlarged/growth on testicle??

My fiance has one testicle that has a growth type thing on it. he has had it checked out by the doctor before but I cant remember what the doctor said it was called(and my fiance isnt home right now to ask him). The condition can be hereditary (his brother has it too) or I think he said it can be caused by childhood trama (ie riding bikes a lot). The growth has double in size over the last 5 yrs or so and now is as large as the testicle itself, making it almost apprear as if there are 3 testicles, sometimes it becomes very sore also, especialy after . I am wondering becuase I am trying to research some stuff about infertility. The doctor said that this abnormality could cause him to be infertle. and so far we have not been able to get pragnant,