For about 4 years ive known that there is a lump on the back side my left testicle seems as if its connected to the top part of the epididymis. doesnt cause any serious pains, but does cause occasional discomfort. could it be cancerous?

Spermatocele: Spermatocele. Also known as a spermatic cyst or epididymal cyst, spermatocele is a typically painless, noncancerous (benign), fluid-filled sac in the scrotum, usually above the testicle. There are other causes of scrotal masses, though and a Dr should examine you thoroughly to rule out other more serious problems: epididymitis, hernia, varicocele, tumor.