Interpreting MR PI-RADs is quite complicated with many variables considered by the evaluator. Let's look at the little I know, then compare your data and mine,

In one published study I looked at, a PI-RADs score of 4 and above had sensitivity of 92% for detection of high Gleason cancer (Gleason 4 or 5), although that was early work. It quickly got more sophisticated, as I noted when I look at my data.

You have one lesion identified, PI-RADS 4, and a PSA of 10.

In my case, the MRI identified a suspicious lesion, PI-RADS 4/5. My PSA was lower than yours at 6.9 (but had been rising several years).

We next went to ultrasound guided systematic biopsy, and found 10 of 13 biopsies were positive for cancer. Two were Gleason 9, and involving > 50% of the biopsy tissue. In other words, high grade, high risk disease, and lots of it.

So, when did my cancer start? Looking at longitudinal PSA, it was probably discoverable at least 5 years earlier if we were prompted by PSA tracking. I think I was lulled a little by the % free data. I doubt if those % free guidelines are well established, I should have known better

Do you happen to have some longitudinal tracking data for your PSA levels? That's the other thing I would like to see.

I'm not going any further with your data. I have no expertise in MRI. That's well beyond my pay grade. I hope my experience revealed in the data is helpful to you on your current journey.