Focal Signet Ring-Like Prostate Adenocarcinoma Detected on Microultrasound in the Setting of Negative Multiparametric Magnetic Resonance Imaging: A Case Report.

The ExactVU microultrasound (microUS) (Exact Imaging, Markham, ON, Canada) is a novel imaging modality that incorporates a standardized lesion classification system known as Prostate Risk Identification using Micro-Ultrasound (PRIMUS) to detect prostate cancer lesions. Here, we report a case of a 65-year-old patient diagnosed with Gleason 5+4 acinar adenocarcinoma with focal signet ring-like (mucinous) features identified on microUS that was not visualized on multiparametric magnetic resonance imaging (mpMRI). This case highlights microUS as a promising tool to improve cancer detection when used in conjunction with mpMRI, as well as the need for further research regarding unconventional prostate cancer histologic variants.