I am 36 and two years ago I actually had my right testicle removed (radical right orchiectomy) due to testicular cancer. From what my urologist told me, usually masses that are exterior are 90% probable as non-cancerous while interior masses are 90% probable to be malignant. Of course, there are exceptions and this IS NOT a rule.
Mine was found during a routine pre-vascectomy consultation when we ended the session with the ole manual touch and feely test, which went from the usual 5 uncomfortable and awkward seconds to well over 20. It was then that I knew something was up, and when he said those words I shall remember forever, "you have a mass in your right testicle", I nearly passed out on the floor and was sick to my styomache all at once, etc.
The whole experience changed my perspective on life.
If anyone has any questions on this please PM me, and DO check yourself. As it turned out I would have never felt my tumors since they were well inside the testicle so it would not have mattered anyway for me, and the type of cancer I had did not produce markers that would show up in a blood screen so they could not tell that ay either. In the end to ultimately tell if something is cancerous or not, despite all of our modern technology, they still have to biopsy and get their handfs on it to tell for sure. By they way, testicles are not the hard balls we like to think of them as and therefore do not biopsy very well. Most of the time they opt to harvest the one testicle (if only one is suspect) to be safe and do the biopsy to confirm.
In the case of the original poster of this thread.... GO TO A UROLOGIST TO GET CHECKED!!! It has been some time now since your original post and hopefully you have done so. Don't do the ostrich and stick your head in the sand... in the end "it is what it is" and you will have to handle it accordingly. This type of cancer is the easiest to cure and responds very well to radiation so you shouldn't have to have chemotherapy treatments unless it has progressed into the lungs(which can not be subjected to radiation) or the brain.
First things first... go to the Urologist dude, a good one that is highly regarded!
-poke