A Histopathologic Assessment of Prostate Ductal Anatomy in Relation to Micro-ultrasound

To analyze whole-mount (WM) pathology slides and to evaluate prostate ductal anatomy as a potential contrast mechanism for visualization of prostate cancer using micro-ultrasound.

Ten men scheduled to undergo radical prostatectomy for prostate cancer (PCa) were enrolled in an IRB-approved study. After prostatectomy, prostates were grossed, sectioned, and stained. All clinically significant PCa lesions were annotated by an experienced pathologist. The scanned slides were then analyzed using a custom computer vision script (MATLAB) to identify and quantify ductal features. Using the annotated lesions, binary masks were made to delineate benign and PCa groups. A color thresholding step was then applied to the tissue within each mask to select the white space where the prostate ducts are located. We extracted 2 main features as follows: the duct equivalent diameter and the ductal ratio, defined as the proportion of tissue area occupied by prostate ducts.

A total of 54 slides were processed, with 145,150 benign and 9245 PCa ducts identified. The mean equivalent diameter of benign ducts was 155.7 ± 147.8 µm. PCa ducts had a mean equivalent diameter of 129.4 ± 94.3 µm. The average ductal ratio for benign tissue was 0.086 ± 0.029 and 0.039 ± 0.017 for PCa tissue.

Prostate ducts are large enough to be resolved on micro-ultrasound but too small for conventional ultrasound. In addition, PCa tissue exhibits an approximate 50% reduction in ductal ratio, which highlights the potential of ductal anatomy as a contrast mechanism for PCa visualization using micro-ultrasound.