Prevalence of prostate cancer in PI-RADS version 2.1 T2-weighted transition zone 'nodule in nodule' and 'homogeneous mildly hypointense area between nodules' criteria: MRI-radical prostatectomy histopathological evaluation.

• The prevalence of clinically significant prostate cancers in PI-RADS v2.1 'nodule in nodule' was low (5-8%, 95% CI: 0.1-17.9%). • Clinically significant prostate cancer was only detected in the 'nodule in nodule' variant when the inner nodule showed absent or incomplete encapsulation ('atypical nodule') with marked restricted diffusion. • 'Homogeneous mildly hypointense area between nodules' is likely benign with no cancers identified in the current study, however, with a wide 95% CI due to low prevalence.