If I (or you, or someone) had testicular cancer but never knew about it, how long could I live with it before I died?
Assume I never had any hint it was there and never sought any medical treatment, even at the very end when the pain was no doubt unbearable.
The reason I ask is because I understand that it spreads “relatively quickly”, but no one ever says how quickly that is. I just want a gauge in comparison to other cancers like lung, kidney, et cetera.
By the way I’m not asking this because I think I have it. It is just out of curiosity, so please no “go see a doctor” responses 
It depends on the type of testicular cancer. Just off the top of my head, there are seminomas, choriocarcinomas, yolk sac tumors, teratomas and mixed cell tumors. There’s almost certainly more categories than that. Also very important in determining the average life expectancy post-diagnosis are the stage and grade of the tumor when diagnosed, any expressed tumor markers, cytogenetics and what treatments are tried.
The doctor’s best guess when my brother died of untreated testicular cancer was that it had metastasized a few months earlier and that he’d had the cancer for at least a year.
Testicular cancer is considered relatively nonlethal, since it’s generally treatable if it hasn’t metastasized: