Presentation
Accidentally discovered metastatic deposits on routine lumbar spine MRI; elevated PSA level.
Patient Data
The left peripheral zone of the prostate shows an ill-defined ovoid mass with underlying contour bulge, yet not breaching the prostatic capsule with no obvious infiltration of the periprostatic fat, neurovascular bundles or seminal vesicles.
This lesion measures 2 x 2.5 x 3 cm in its maximal orthogonal dimensions and exhibits low signals on T2 WIs and ADC, with bright signals on DWI (b value = 1500 s/mm2), as well as avid enhancement on early dynamic post-contrast series (positive DCE) and washout on delayed post-contrast series [PIRADS 5].
Single voxel MRS reveals elevated Choline peak at 3.2 ppm with increased Choline+Creatine to Citrate ratio, highly suggestive of malignancy.
Case Discussion
According to PIRADS V2 (Prostate Imaging Reporting And Data System - Version 2), the overall PI-RADS assessment category that ultimately determines the level of suspicion for clinically significant prostate cancer for peripheral zone abnormality is scored by using a 5-point scale depending on DWI-ADC combination, whereas for transitional zone abnormality depends on T2-weighted MR imaging.
In our case, the left peripheral zone mass corresponds to a score of 5 based on being a "focal abnormality that is markedly hypointense on ADC maps and markedly hyperintense on high–b value diffusion-weighted MR images and measures more than 1.5 cm in greatest dimension". Additionally, the lesion scores as 5 on T2 WIs as well based on being "circumscribed, homogeneous moderately hypointense mass confined to the prostate and more than 1.5 cm in greatest dimension", with positive dynamic contrast enhancement (DCE).
MRS (MR spectroscopy), although omitted in PIRADS scoring, yet when added to other MRI parameters, it improves the detection rate and confidence level.
The diagnosis was confirmed on histopathology and the patient started chemotherapy shortly after.
The initial presentation was with low back pain and left sciatica, for which lumbar spine MRI was requested and metastatic deposits (sclerotic bone deposits and pathological lymphadenopathy) were accidentally discovered [Radiopedia case: rID: 70718 / "Metastasis on routine lumbar spine MRI"].
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