cyst v. cancer

So yesterday I was feeling my testicles in the shower and noticed a very tiny, basically BB-sized lump at the bottom/back part of my right teste. Of course, immediately afterwards my mind was flooded with fears of testicular cancer. However, today I had the chance to self-examine myself a little bit better, and it doesn't seem as if the bump is actually on my testicle. I can move it around, and when my testicles are hanging straight down I can always pinpoint it with my finger, but during self-examinations, it doesn't always show up.  Moreover, it's not hard--only somewhat firm and squishy. I can kind of grab hold of it. Aren't tumors typically rather hard and directly on the testicle? There is no pain, no aching, my testicles don't seem swollen or heavier than usual. I was inspected by a doctor on a checkup at the end of April, and he said there was nothing out of the ordinary. Naturally I know that your medical opinion is no substitute for an actual checkup and scan, and as soon as I can make it to a urologist, I will. I'm seeing one next week. In the meantime, I was just wondering if you could tell me a little more about epididymal cysts and testicular cancer--a little quasi-bedside manner, if you will. My father was just diagnosed with prostate cancer last week, so I've been pretty worried as is. Anyway, whatever you could possibly tell me while I wait to go see a doctor in person, I'd be so appreciative.

[Ash Tewari, MD, M.Ch.]

Cysts in general are fluid filled sacs. This happens when some duct or gland or secreting epithelium gets blocked or trapped and is not able to drain freely. The epididymis and cord area could have cysts, spermatoceles, small lipomas, and dilatations of the veins called varicoceles.
From what you have described this may not be a testicular tumor. varicoceles are dilated veins- ususally multiple veins which can be felt when standing, but may disappear (in early cases) when lying down. However varicoceles would not typically be dicrete lumps like a pellet or a BB.