Multiparametric MRI of the anterior prostate gland: clinical-radiological-histopathological correlation

Anterior prostate cancer (APC) is defined as a tumour in which more than half of malignant tissue is located anterior to the urethra. APCs are increasingly recognized as clinically important, particularly in patients undergoing active surveillance and for patients with negative non-targeted systematic transrectal ultrasound (TRUS)-guided biopsies but with persistent clinical suspicion of cancer. Multiparametric (mp) MRI has a crucial role for the diagnosis of anterior tumours, eventual histological sampling of suspicious lesions using image-guided targeted biopsy techniques, and potentially, to improve local staging of disease. mpMRI is accurate for the detection of APC and for differentiation of tumour from other anterior prostatic structures including benign prostatic hyperplasia (BPH) and the anterior fibromuscular stroma (AFMS). Characterization and reporting of APC should rely on the recently revised Prostate Imaging and Data Reporting System (PI-RADS) version 2.0 document. T2-weighted (T2W) imaging is emphasized as the determining sequence for assessment of the anterior prostate and specific features for APC on T2W imaging include: ill-defined/spiculated margin, lenticular shape, anterior/inferior location, and growth pattern (invasion of urethra or AFMS and crossing midline). Functional imaging, mainly with diffusion-weighted imaging, is also contributory and improves the sensitivity for detection of APC compared to T2W imaging alone. APCs commonly show positive surgical margins after radical prostatectomy and staging of disease extent using conventional clinical parameters is limited. mpMRI may have a future role to improve local staging of APC. This review illustrates the importance of mpMRI in APC using a clinical-radiological-histopathological approach.