Bummer! https://www.sciencedirect.com/science/article/abs/pii/S1078143919304454
The presence of 4 of those 4+4 cores decreases the chances that less cancer will be found than those cores indicate. It's interesting that you mention a PSMA PET scan but no MRI. I assume, though, with 18 cores, that it was an MRI-guided biopsy. Multiparameter MRI's with good interpretation can give a clearer picture in some ways than biopsies, they're just later to the game of diagnosis and treatment. (12 of the biopsy samples were systematic, one per region, and the remaining six were targeted. The 4 most significant were likely two each in nodules identified on the MRI and guided by ultrasound.
In the larger scheme of things, from diagnosis to surgery in 12 weeks is not slow :-). A lot has happened quickly. If your situation is like mine, you have a lot of catching up to do--understanding the nature of the disease, the impact and recovery from surgery and how to manage it, getting your affairs in order given these new realities and possibilities, spending time with those close to you adjusting and helping them adjust, and enjoying this last summer with a prostate in the best ways possible.