I don't have any studies to cite yet. Not necessarilly claiming it causes cancer but I definately believe it can speed up cancers that might have taken years to develope.
The use of performance enhancing drugs or PEDs is basically all about sped up recovery. That's why many are able to gain muscle mass faster and why many never seem to run out of gas. It's not so much about adding muscle to the body as it is helping the body recover by repairing cells/muscle faster decreasing rest time and thus increasing the amount of workouts or physical work you can do(on your sport).
Let's say you have cancer cells in their infancy. But with PEDs in your system which help repair existing cells wouldn't they also help speed up or even trigger the growth of cancer cells? 60 Minutes(yeh I know) did a thing on growth hormones(gh) in which a doctor said gh and multiplying cells ie something like cancer might not be a good combination. At the sametime your are giving normal cells a boost you also might be boosting cancer cells.
But the only people I personally know of that have/had testicular cancer were/are gym rats or involved in sports. Also by coincidence have gotten it by their late 20s/early 30s just like Lance.
You provide an interesting theory and by itself, it is very interesting. Yet, as much as cancer(s) have been atributted to steroid use, I don't remember ever reading anything pointing to any particular cancer on it's own, much less testicular cancer.
As for the speed or time sequence of any cancer spreading or growing inside an individual, each varies differently, yet some what similar with each case.
Let's not forget that US figure skater Scott Hamilton also contracted testicular cancer as well and I rather doubt that he had ever used illegal drugs.
In everything that I have read on this topic, I have not seen anything that stated anything in reference to illegal sports drugs speeding cancer(s). So, I would be hesitant in making statements without any imperical literature to support them.
On another note:
In today's newpaper, it was announced that the feds are going to review the video footage from the restraunt cameras where Tyler Hamilton and Lance Armstrong accidently ran into one another this weekend.
Tyler Hamilton immediately went and reported to his lawyers, who reported to the authorities about the incident. Sad case of affairs considering they were once friends.