Multiparameter magnetic resonance imaging features of prostatic malakoplakia.

Objective: To summarize the multiparameter magnetic resonance imaging (mpMRI) features of prostatic malakoplakia.

Methods: Eleven patients (median age 62 years; IQR 59-71 years) with pathologically confirmed prostatic malakoplakia were included in this study. MpMRI features of the lesions were retrospectively reviewed and summarized.

Results: The Prostate Imaging-Reporting and Data System (PI-RADS) scores of the patients were 4 or 5, with a medium diameter of 3.7 cm (IQR 2.0-5.2 cm). All the lesions involved the peripheral zone, of which 3 cases (3/11, 27.3%) involved the transition zone simultaneously. A diffuse symmetrical distribution was found in 5 cases, a focal distribution in 5 cases, and a focal symmetrical distribution in 1 case. Both the surgical capsule and prostatic margin were bulged and compressed, but no signs of infiltration were found. Nearly all the lesions had moderate hypointensity on T2-weighted images and slightly higher signal intensity on T1-weighted images. Among the lesions, early enhancement occurred in all cases, prolonged enhancement occurred in 8 cases, and ring enhancement persisted in 1 case. All lesions displayed periprostatic enhancement in the delayed phase.

Conclusions: Lesions distributed diffusely and symmetrically in the peripheral zone with preserved surgical capsule and margin are characteristic features of malakoplakia as opposed to cancer, especially in those with slightly high T1 signal intensity and delayed periprostatic enhancement. Those locally distributed lesions with the above signs should also be suspected.

Advances in knowledge: Prostatic malakoplakia are more likely to distribute diffusely and symmetrically, with slightly high T1 signal intensity and delayed periprostatic enhancement.