Prostate cancer - staging

Biparametric MRI of the prostate bpMRI

Findings:

Quality: no major artefacts

Prostate size: 42 x 38 x 40 mm (CC x AP x ML)  ≈33 mL

Haemorrhage: none

Peripheral zone (PZ): diffusely hypointense bilaterally, especially posterior zone from base to apex, there is some residual heterogeneous signal in the apical anterior zones

Transition zone (TZ): some BPH nodules in the anterior transition zone, otherwise diffusely hypointense, especially within the posterior transition zone with indistinct margins of the pseudocapsule

Prostate margin: broad capsular contact

Neurovascular bundles: probably involved

Seminal vesicles: extension of T2w hypointensity and some diffusion restriction along the ejaculatory ducts above the base and within the seminal vesicles suggestive of seminal vesicle invasion

Lymph nodes: oval external iliac lymph nodes (up to 5 mm size, fatty hilum, smooth margins)

Pelvic bones: small lesion in the right femoral head very likely a bone island, no definite signs of bony metastasis

Impression:

Histologically proven prostate cancer with infiltration of both lobes especially posterior peripheral and transition zones (basal to apical) with the involvement of the central zone.

An extraprostatic extension is likely.

Probable invasion of both seminal vesicles.

MRI putative stage: cT3bNxMx

Key findings:

Marked hypointensity can be seen in T2w images covering up 70-80% of the prostate with smudged borders (red arrows) resembling the “erased charcoal sign”. However, it has been described that gland shrinkage, atrophy and fibrosis following androgen deprivation induce T2 signal reduction in the normal peripheral zone and this compromises the distinction of tumour margins ^7-10.

There is corresponding hypointensity on ADC (red arrowheads), which can be best appreciated in the apex because there is some residual normal-appearing glandular tissue in the anterior and left lateral prostate segments (blue arrows).

Not much can be seen on DWI (b1400) images (orange arrowhead), this is very likely to be due to the patient receiving androgen deprivation therapy.

Marked signal loss within the inferior portions of the seminal vesicle (green arrowheads).

Findings from the previous biparametric MRI of the prostate (bpMRI) are illustrated.

Biopsy results:

Histology of the systematic biopsy performed about 6 months earlier showed an acinar adenocarcinoma (modified Gleason score 4+3=7a, grade 2) within 12/12 cores. There was also perineural nerve sheath infiltration bilaterally.