Re: very worried could be testicle cancer?
Veins in the testicles can become enlarged due to a poor valve, this is very common especially on the left testicle. You say you are very active, soreness may be a different but related problem caused by the testicles bouncing into each other over and over from lots of physical activity. The left one, again, is most often sore because it tends to hang lower in many males and thus bounces more.. try wearing a jock strap during sports, or at least briefs instead of boxers when you are doing prolonged activity. Wearing these has also been known to reduce vein swelling. I'm not sure what the oval is you're talking about, whether it's a vein or what, you can see a doctor to be safe but try wearing what I suggested to see if that relieves soreness.