Multiparametric magnetic resonance imaging characteristics of normal, benign and malignant conditions in the prostate

Objectives: To identify the multiparametric magnetic resonance imaging (mpMRI) characteristics of normal, benign and malignant conditions in the prostate. Methods: Fifty-six histopathological whole-mount radical prostatectomy specimens from ten randomly selected patients with prostate cancer (PC) were matched with corresponding transverse mpMRI slices. The mpMRI was performed prior to biopsy and consisted of T2-weighted imaging (T2-WI), diffusion-weighted imaging (DWI), dynamic contrast-enhanced imaging (DCE) and magnetic resonance spectroscopic imaging (MRSI). Results: In each prostate specimen, a wide range of histopathological conditions were observed. They showed consistent but overlapping characteristics on mpMRI. Normal glands in the transition zone showed lower signal intensity (SI) on T2-WI, lower ADC values and lower citrate peaks on MRSI as compared to the peripheral zone (PZ) due to sparser glandular elements and more prominent collagenous fibres. In the PZ, normal glands were iso-intense on T2-WI, while high SI areas represented cystic atrophy. Mimickers of well-differentiated PC on mpMRI were inflammation, adenosis, HG-PIN and post-atrophic hyperplasia. Conclusion: Each prostate is a unique mix of normal, benign and/or malignant areas that vary in extent and distribution resulting in very heterogeneous characteristics on mpMRI. Understanding the main concepts of this mpMRI-histopathological correlation may increase the diagnostic confidence in reporting mpMRI. Keypoints: • In each prostate specimen a wide range of histopathological conditions was observed. • Interpretation of mpMRI may be difficult because benign conditions may mimic PC. • High signal intensity areas in the PZ on T2-WI represented cystic atrophy. • The TZ showed sparser glands and more collagenous fibres than the PZ.