Histomorphological analysis of false positive PI-RADS 4 and 5 lesions

Introduction: Multiparametric magnetic resonance imaging (mpMRI)/ultrasound fusion-guided biopsy, in short "targeted biopsy (TB)", is becoming more attractive as it improves the detection of clinically significant prostate cancer (CaP). The accuracy of fusion-guided biopsies is limited due to false positive radiological findings as well as to histological evidence for cancer in radiologically inconspicuous regions of the prostate. We aimed to analyze histomorphological findings on mpMRI lesions highly suspicious for CaP classified as PI-RADS 4 or PI-RADS 5 (Prostate Imaging - Recording and Data System) but cancer-negative in the biopsy of this region of interest (ROI), and to compare them with findings in radiologically inconspicuous regions.

Materials and methods: We re-evaluated prostate biopsies from 57 patients who underwent TB in combination with systematic standard biopsy (SB) from June 2017 to July 2018 at the University Hospital Schleswig Holstein Campus Luebeck. Out of 143 ROIs, 34 PI-RADS 4/5 cancer-negative lesions were identified and subjected to comprehensive histomorphological reevaluation. Contralateral cancer-negative SBs were used as control. Chi-square test was used for statistical analysis.

Results: The frequency of histomorphological alterations including stromal, glandular, vascular, and inflammatory alterations were 97% and 79.2% in prostatic tissues from cancer-negative TBs and SBs, respectively. Stromal, glandular, and inflammatory alterations were present in the majority of biopsies from both TBs and SBs. Statistical analysis revealed no significant difference between TBs and SBs with regard to stromal, glandular, and inflammatory alterations. However, vascular abnormalities were exclusively detected in TBs (18.2%).

Conclusion: The frequency of histomorphological alterations is slightly higher in prostate tissues from TBs compared to SB. Only vascular alterations seem to be distinct for TBs. However, it has to be assumed that additional factors influence the false-negative rate of mpMRI/ultrasound fusion-guided TB.