Growth Patterns of Prostate Cancers Undetected by Prostate 3T Multiparametric MRI

Abstract

Background/aim: The multiparametric magnetic resonance imaging (mpMRI)-ultrasound (US) fusion targeted biopsy (TB) is a useful diagnostic device for men with suspected prostate cancer (PC) and can increase the detection rate for clinically significant PCs (csPC). However, few studies have shown pathological findings of undetectable csPCs on the prostate mpMRI.

Patients and methods: This study investigated the growth patterns of csPC undetected in prostate mpMRI. The study enrolled 248 patients with suspected PCs and ≥PI-RADS 2 lesions, who then underwent mpMRI-US fusion TB and nearly prostate-mapping systematic biopsies (SB). A total 248 biopsies included 404 regions of interest in TB and 2976 mapping-regions in SB.

Results: The detection rates of csPC, defined as PC grade group (GG) ≥2, were 42% in TB and 44% in SB, and the highest detection rate was 50%, using both TB and SB. Approximately 79% of PI-RADS 3/4/5 with any PC showed csPC. A total 201 PI-RADS 3/4/5 lesions showed benign prostatic hyperplasia, lymphocytic prostatitis, or fibromuscular stroma only in the core tissues. Notably, 22 csPCs detected in SB but undetected in prostate mpMRI preferentially showed a pattern of mixed well-formed and fused PC glands. The other patterns including cribriform glands and poorly formed glands with intracytoplasmic vacuoles were also seen. Approximately 85% of the 22 csPCs showed tumor volume less than 50% of core tissues.

Conclusion: Changes in prostatic stroma amounts, inflammation severity, tumor volume and growth patterns of PC glands affected the detectability of prostate mpMRI.

Keywords: Multiparametric MRI; biopsy; fusion; pathology; ultrasound.

Figure 1. Histopathology of Prostate Imaging–Reporting and Data System (PI-RADS) 4/5 lesions in targeted biopsies with absence of prostatic cancers. (A) nodular hyperplasia; (B) fibromuscular stroma only; (C) lymphocytic prostatitis. Sections were stained with hematoxylin and eosin.

Figure 2. Pathological findings of undetectable Prostate Imaging–Reporting and Data System (PI-RADS) lesions. (A, B) cribriform glands; (C) ductal adenocarcinoma; (D) fused gland; (E) glomeruloid glands; (F) Gleason pattern 5 tumor, with lack of gland formation. Sections were stained with hematoxylin and eosin.