Prostate imaging features that indicate benign or malignant pathology on biopsy

Abstract

Accurate diagnosis of clinically significant prostate cancer is essential in identifying patients who should be offered treatment with curative intent. Modifications to the Gleason grading system in recent years show that accurate grading and reporting at needle biopsy can improve identification of clinically significant prostate cancers. Extracapsular extension of prostate cancer has been demonstrated to be an adverse prognostic factor with greater risk of metastatic spread than organ-confined disease. Tumor volume may be an independent prognostic factor and should be considered in conjunction with other factors. Multi-parametric magnetic resonance imaging (MP-MRI) has become an increasingly important tool in the diagnosis and characterization of prostate cancer. MP-MRI allows T2-weighted (T2W) anatomical imaging to be combined with functional and physiological assessment. Diffusion-weighted imaging (DWI) has shown greater sensitivity, specificity and negative predictive value compared to prostate specific antigen (PSA) testing and T2W imaging alone and has a more positive correlation with Gleason score and tumour volume. Dynamic gadolinium contrast-enhanced (DCE) imaging can exhibit difficulties in distinguishing prostatitis from malignancy in the peripheral zone, and between benign prostatic hyperplasia (BPH) and malignancies in the transition zone (TZ). Computer aided diagnosis utilizes software to aid radiologists in detecting and diagnosing abnormalities from diagnostic imaging. New techniques of quantitative MRI, such as VERDICT MRI use tissue-specific factors to delineate different cellular and microstructural phenotypes, characterizing tissue properties with greater detail. Proton MR spectroscopic imaging (MRSI) is a more technically challenging imaging modality than DCE and DWI MRI. Over the last decade, choline and prostate-specific membrane antigen (PSMA) positron emission tomography (PET) have developed as better tools for staging than conventional imaging. While hyperpolarized MRI shows promise in improving the imaging and differentiation of benign and malignant lesions there is further work required. Accurate reading and interpretation of diagnostic investigations is key to accurate identification of abnormal areas requiring biopsy, sparing those in whom benign or indolent disease can be managed by non-invasive means. Embracing and advancing existing technologies is essential in furthering this process.

Keywords: Prostate; benign; imaging; magnetic resonance imaging (MRI); malignant; parametric; qualitative; quantitative.

Figure 1

Capsular irregularity with no clear plane between prostate gland and adjacent anterior rectum at left posterior aspect of gland. T2 imaging.

Figure 2

Crescent of low T2 signal in anterior horn of left mid and basal gland, likely tumour.

Figure 3

Area of high intensity secondary to a TURP defect.

Figure 4

Utilizing diffusion weighted-imaging. (A) long b axial image, hyperintense tumour lesion right posterolateral zone, (B) hypointense lesion on ADC image.

Figure 5

Reduced enhancement of left posterior peripheral zone on DCE, concerning for T4 disease.

Figure 6

BPH with stromal nodules.

Figure 7

Nodular hyperplasia of TZ with low probability of significant tumour.

Figure 8

Similarities between stromal nodules and tumour tissue. (A) T2 hypointensity at right apex; (B) hyperintensity of same lesion on DCE, likely tumour.

Figure 9

Post-biopsy prostatic haemorrhage.

Figure 10

17 mm cystic lesion at right peripheral zone apex.

Figure 11

Crescent-shaped urethral diverticulum surrounding membranous urethra.

Figure 12

Prostatitis identified on MRI.

Figure 13

Prostatic atrophy in peripheral zone on T2-MRI.

Figure 14

T2 image with medial-mid right peripheral zone wedge-shaped hypodensity suggestive of fibrosis. Incidental midline Mullerian duct remnant.