histopathology slice as well as mounting with either aligned or misaligned left-right orientation. To account for this variability, an expert indicated the gross rotation angle and whether the slice requires left-right flipping. The whole-mount slices in C1 and quadrants sections in C2 were stained using Hematoxylin & Eosin (H&E) and were digitized at 20x magnification (pixel size 0.5 $\mu m$). Pseudo-whole mounts were generated for the images in C2, by stitching adjacent quadrants as described in [@singanamalli_identifying_2016].

*Labels:* Our expert radiologist (PG) outlined the prostate on MRI, $\mathcal{M}^{Pr}$, while our expert pathologist (CK) outlined the prostate, $\mathcal{H}^{Pr}$, and the cancer on the high-resolution scanned images of the histopathology specimen. Two hundred fifty-seven matching anatomic landmarks were picked on both histopathology and radiology images for a subset of 12 subjects, targeting 3 landmarks for each corresponding pair of histopathology and MRI slices. Examples of anatomic landmarks include benign prostate hyperplasia nodules, ejaculatory ducts, predominant glands, etc. The urethra was outlined on 22 studies in cohort C1 and the 16 studies in cohort C2. Outlining the urethra on MRI is relatively straightforward at the apex of the prostate, yet it becomes challenging towards the base. Thereby, often urethra annotations are available on 