Interpreting Prostate Multiparametric MRI: Beyond Adenocarcinoma - Anatomical Variations, Mimickers, and Post-Intervention Changes

Abstract

Prostate magnetic resonance imaging (MRI) is an essential tool in the diagnostic pathway for prostate cancer. However, its accuracy can be confounded by a spectrum of noncancerous entities with similar radiological features, posing a challenge for definitive diagnosis. This review synthesizes current knowledge on the MRI phenotypes of both common and rare benign prostate conditions that may be mistaken for malignancy. The narrative encompasses anatomical variants, other neoplastic processes, inflammatory conditions, and alterations secondary to medical interventions. Furthermore, this review underscores the critical role of MRI quality in diagnostic accuracy and explores the emerging contributions of artificial intelligence in enhancing image interpretation.

Figure 1:

Multiparametric MRI of a 60-year-old man with a mildly elevated prostate-specific antigen level of 4.29 ng/mL. Axial (A), sagittal (B), and coronal (C) T2-weighted imaging show hypointense appearance of the normal central zone bilaterally (arrows). (D) Axial high b-value diffusion-weighted imaging showing normal central zone anatomy as bilateral slightly hyperintense areas (arrows). (E) Axial apparent diffusion coefficient (ADC) map showing normal central zone anatomy as bilateral low signal intensity areas (arrows). (F) Axial dynamic contrast-enhanced image lacks early contrast enhancement on the area corresponding to the central zone.

Figure 2:

Multiparametric MRI of a 62-year-old man with an elevated prostate-specific antigen level of 8.83 ng/mL. Axial (A), sagittal (B), and coronal (C) T2-weighted imaging show a prominent hypointense appearance of a left central zone lesion (arrow). Axial high b-value diffusion-weighted imaging (D) and apparent diffusion coefficient (ADC) map (E) showing an asymmetrical abnormal diffusion restriction within the left central zone (arrow). (F) Axial dynamic contrast-enhanced image shows focal early contrast enhancement on the left side that corresponds to a central zone lesion (arrows).

Figure 3:

Multiparametric MRI of a 61-year-old man with a mildly elevated prostate-specific antigen level of 4.4 ng/mL. Axial (A), sagittal (B), and coronal (C) T2-weighted imaging show a prominent hypointense area on the anterior side of the prostate gland which corresponds to the anterior fibromuscular stroma (arrows). (D) Axial high b-value diffusion-weighted imaging showing normal anterior fibromuscular stroma anatomy as a small hypointense area (arrow). (E) Axial apparent diffusion coefficient (ADC) map showing normal anterior fibromuscular stroma anatomy as a low signal intensity area (arrow). (F) Axial dynamic contrast-enhanced image showing absent contrast enhancement on the area corresponding to the anterior fibromuscular stroma (arrow).

Figure 4:

Multiparametric MRI of a 65-year-old man with an elevated prostate-specific antigen level of 8.3 ng/mL. Axial (A), sagittal (B), and coronal (C) T2-weighted imaging show a hypointense lesion on the midline apical-mid anterior transition zone which is in close proximity to the anterior fibromuscular stroma (arrow). (D) Axial high b-value diffusion-weighted imaging showing the lesion as a hyperintense area (arrow). (E) Axial apparent diffusion coefficient (ADC) map showing the lesion as a hypointense area (arrow).

Figure 5:

A 66-year-old patient with prominent bulbourethral glands (Cowper’s glands) which appear hypointense on axial (A), sagittal (B), coronal (C) T2-weighted imaging (arrows) similar to prostate cancer, similarity in imaging characteristics could be a pitfall during prostate MRI interpretation. High b-value diffusion-weighted imaging (D) and apparent diffusion coefficient (ADC) map (E) may also indicate a diffusion restriction (arrows). Minimal early contrast enhancement can also be seen on dynamic contrast enhancement images (F) (arrows).

Figure 6:

Multiparametric MRI of a 68-year-old man with an elevated prostate-specific antigen level of 5.47 ng/mL. Axial (A), sagittal (B), and coronal (C) T2-weighted imaging, axial high b-value diffusion-weighted imaging (D), apparent diffusion coefficient (ADC) map (E), and dynamic contrast-enhanced image (F) show signal void areas in the left apical peripheral zone which correspond to calcifications (arrow).

Figure 7:

Multiparametric MRI of a 60-year-old man with an elevated prostate-specific antigen level of 6.9 ng/mL. Axial (A), sagittal (B), and coronal (C) T2-weighted imaging show a well-demarcated right apical peripheral zone lesion which corresponds to an ectopic benign prostatic hyperplasia nodule (arrow). (D) Axial high b-value diffusion-weighted imaging showing the ectopic benign prostatic hyperplasia nodule as a hyperintense area (arrow). (E) Axial apparent diffusion coefficient (ADC) map showing the ectopic benign prostatic hyperplasia nodule as a hypointense area (arrow). (F) Axial dynamic contrast-enhanced image showing early focal enhancement on the area corresponding to the ectopic benign prostatic hyperplasia nodule (arrow).

Figure 8:

Multiparametric MRI of a 75-year-old man with a prostate-specific antigen level of 3.8 ng/mL. Axial (A), sagittal (B), and coronal (C) T2-weighted imaging show an anteriorly located benign prostatic hyperplasia nodule with a cystic degeneration. The fluid content of the nodule gives it the high intensity appearance (arrow). (D) Axial high b-value diffusion-weighted imaging showing the benign prostatic hyperplasia nodule with a cystic degeneration as a hypointense area (arrow). (E) Axial apparent diffusion coefficient (ADC) map showing the benign prostatic hyperplasia nodule with a cystic degeneration as a hyperintense area (arrow).

Figure 9:

Multiparametric MRI of a 66-year-old man with a prostate-specific antigen level of 1.5 ng/mL. (A) Axial T2-weighted imaging shows a hypointense vascular structure (arrowhead) surrounded by hyperintense periprostatic fat tissue (arrow) which make up the neurovascular bundle. (B) Axial high b-value diffusion-weighted imaging shows the area corresponding to the neurovascular bundle as hypointense (arrow). (C) Apparent diffusion coefficient (ADC) map showing low signal intensity corresponding to the vascular structures within the bundle (arrow). (D) Dynamic contrast-enhanced image shows enhancement of the arterial component (asterisk) of the neurovascular bundle (arrow).

Figure 10:

A 67-year-old patient with a prostate-specific antigen level of 2.5 ng/mL. There is a dilated periprostatic vein which appears hypointense on axial (A), sagittal (B), coronal (C) T2-weighted imaging (arrows). High b-value diffusion-weighted imaging (D) lack diffusion restriction and apparent diffusion coefficient map (E) may also show a hypointense area (arrows). Dynamic contrast enhancement images (F) lack early contrast enhancement (arrow).

Figure 11:

A 68-year-old patient with a prostate-specific antigen level of 4.5 ng/mL. There is a phlebolith seen as a hypointense area which is located more caudally and anteriorly to the prostate apex on axial (A), sagittal (B), coronal (C) T2-weighted imaging (arrows). High b-value diffusion-weighted imaging (D) lacks diffusion restriction and apparent diffusion coefficient map (E) also show a hypointense area (arrows). Dynamic contrast enhancement images (F) lack early contrast enhancement (arrow).

Figure 12:

A 67-year-old patient with a mildly elevated prostate-specific antigen of 4.1 ng/mL. There is a lesion in the left apical-mid anterior transition zone. It is a well-demarcated and multi-lobar lesion with heterogenous signal intensity and a hyperintense cystic component (asterisks) on axial (A), sagittal (B), coronal (C) T2-weighted imaging (arrows). High b-value diffusion-weighted imaging (D) and apparent diffusion coefficient (ADC) map (E) show heterogeneous diffusion restriction (arrows). The imaging findings are consistent with Stromal Tumor of Uncertain Malignant Potential (STUMP).

Figure 13:

A 64-year-old patient with an elevated prostate-specific antigen of 7.1 ng/mL. The patient has a midline apical-mid anterior transition zone lesion that is a biopsy-proven mucinous adenocarcinoma of the prostate. It is well-demarcated with high signal intensity on axial T2-weighted imaging (A) and high b-value diffusion-weighted imaging (B) (arrows). Apparent diffusion coefficient (ADC) map (C) shows isointense signal characteristics within the lesion while dynamic contrast-enhanced MRI (D) shows early focal enhancement (arrows).

Figure 14:

A 72-year-old patient with an undetectable serum prostate-specific antigen level. Multiparametric MRI shows diffuse malignant involvement of the prostate with hypointense regions on T2-weighted imaging (T2WI) on axial (A), sagittal (B), and coronal (C) views, and diffusion restriction on high b-value diffusion-weighted imaging (DWI) (D) and the apparent diffusion coefficient (ADC) map (E). Indistinct prostate margins are visible anteriorly (arrows), suggesting extension beyond the gland. Involvement of neighboring structures is indicated by abnormal signal in the rectum wall (asterisks) and the left pubic bone (arrowheads), consistent with small cell carcinoma of the prostate.

Figure 15:

A 62-year-old patient with a prostate-specific antigen level of 2.42 ng/mL. Multiparametric MRI shows well-defined, lobulated lesion with intermittent hypointense rims on axial (A), sagittal (B), and coronal (C) T2-weighted imaging. Marked diffusion restriction is observed on high b-value diffusion-weighted imaging (D) and the apparent diffusion coefficient (ADC) map (E), along with early contrast uptake on dynamic contrast-enhanced MRI (F). Imaging features are suggestive of ductal carcinoma of the prostate.

Figure 16:

A 61-year-old patient with a prostate-specific antigen level of 12.2 ng/mL. Multiparametric MRI reveals asymmetrical enlargement and heterogeneous signal patterns in the left peripheral zone on axial (A), sagittal (B), and coronal (C) T2-weighted imaging (T2WI), along with the heterogeneous signal intensity noted on both the high b-value diffusion-weighted imaging (DWI) (D) and the apparent diffusion coefficient (ADC) map (E) (arrows). There is also a diffuse peripheral rim enhancement observed on dynamic contrast-enhanced MRI (F) (arrow). These features are indicative of acute prostatitis.

Figure 17:

A 63-year-old patient with a prostate-specific antigen level of 4.97 ng/mL who recently had a Bacillus Calmette-Guérin (BCG) induction therapy. The patient has multiple lesions, including the one located in the right apical-mid peripheral zone. The lesion appears hypointense on axial (A), sagittal (B) and coronal (C) T2-weighted imaging (arrows). While the lesion displays diffusion restriction on high b-value diffusion-weighted-imaging (D) and apparent diffusion coefficient (ADC) map (E), it does not have early focal contrast enhancement (F). Imaging findings are suggestive of BCG-associated chronic granulomatous prostatitis.

Figure 18:

A 51-year-old patient with a prostate-specific antigen (PSA) level of 8.1 ng/mL who recently had a urinary tract infection. There is a lesion in the midline apical anterior transition zone, which appear hypointense on T2-weighted axial (A), sagittal (B) and coronal (C) imaging, with no diffusion restriction on high b-value diffusion-weighted imaging (D) and apparent diffusion coefficient (ADC) map (E) (arrows). Unlike prostate adenocarcinoma, prostate abscesses have peripheral rim enhancement (F) (arrow).

Figure 19:

A 64-year-old patient with a prostate-specific antigen level of 6.6 ng/mL who recently had a prostate biopsy which confirmed his prostate adenocarcinoma. The cancerous lesion appears hypointense on T2-weighted axial (A) and sagittal (B) imaging, hyperintense on high b-value diffusion-weighted imaging (C), hypointense signal on apparent diffusion coefficient (ADC) map (D) with early focal enhancement on dynamic contrast-enhanced MRI (E) without hyperintensity on pre-contrast T1-weighted imaging (F) (arrows). The biopsy-associated hemorrhage also appear hypointense on T2-weighted imaging (A), however, it does not display diffusion restriction (C,D) and appear hyperintense on T1-weighted imaging (F) before the administration of contrast (arrowheads). Findings are consistent with bilateral peripheral zone hemorrhage with hemorrhage exclusion sign within the left-sided cancerous lesion.

Figure 20:

A 70-year-old patient with a prostate-specific antigen level of 0.04 ng/mL who was treated with androgen deprivation therapy for a large lesion affecting almost the entire left hemigland. Post-treatment, the gland size reduces, and the prostate appears diffusely hypointense, making the lesion almost indistinguishable on T2-weighted imaging (A). However, the lesion still exhibits diffusion restriction, displaying a hyperintense signal on high b-value diffusion-weighted imaging (B), a hypointense signal on apparent diffusion coefficient (ADC) map (C) along with early contrast uptake on dynamic contrast-enhanced MRI (D) (arrows).

Figure 21:

A 71-year-old patient with a prostate-specific antigen level of 10.9 ng/mL who will be treated with external beam radiation therapy for a lesion located in the left apical-mid transition zone. The lesion appears appear hypointense on T2-weighted imaging (A), hyperintense on high b-value diffusion-weighted imaging (B), hypointense on apparent diffusion coefficient (ADC) map (C), and displays early focal enhancement on dynamic contrast-enhanced MRI (D) (arrows). The fiducial markers that are placed for radiotherapy planning appear signal void on all sequences (arrowheads).

Figure 22:

A 62-year-old patient with a prostate-specific antigen level of 1 ng/mL who received external beam radiation therapy for a lesion located in the left apical-mid peripheral zone. The spacer material appears hyperintense on T2-weighted axial (A), sagittal (B), and coronal (C) imaging without diffusion restriction on high b-value diffusion-weighted imaging and apparent diffusion coefficient (ADC) map (arrows).

Figure 23:

A 70-year-old patient with a prostate-specific antigen level of 23.9 ng/mL. There is a lesion in the right apical-base anterior transition zone which appear hypointense on T2-weighted axial (A) and sagittal (B) imaging, that displays diffusion restriction on high b-value diffusion-weighted imaging (C), and apparent diffusion coefficient (ADC) map (D) (arrowheads). There is a small intraprostatic infiltration of the spacer material in the midline mid peripheral zone (arrows).

Figure 24:

A 70-year-old patient with an undetectable prostate-specific antigen level with a history of external beam radiation therapy and androgen deprivation therapy. Post-treatment MRI displays diffuse hypointensity on T2-weighted imaging, consistent with expected post-radiation changes, without any focal areas of diffusion restriction or significant findings on the high b-value diffusion-weighted imaging and apparent diffusion coefficient (ADC) map. Dynamic contrast-enhanced MRI also does not reveal any areas of concerning enhancement. These findings collectively suggest an absence of recurrent prostate cancer.

Figure 25:

A 77-year-old patient with a prostate-specific antigen level of 5.6 ng/mL with a history of external beam radiation therapy. There is a lesion in the midline to left apical-mid peripheral zone which appears mildly hypointense & heterogeneous on T2-weighted imaging (A), hyperintense on high b-value diffusion-weighted imaging (B) and hypointense on the ADC map (C), with early focal enhancement on dynamic contrast-enhanced MRI (D) (arrowheads). MRI/US fusion-guided biopsy confirmed recurrent prostate cancer.

Figure 26:

A 70-year-old patient with a prostate-specific antigen level of 11.9 ng/mL with a history of brachytherapy. There is a lesion in the midline base anterior transition zone which appears hypointense on T2-weighted imaging (A), hyperintense on high b-value diffusion-weighted imaging (B) and hypointense on the ADC map (C), with early focal enhancement on dynamic contrast-enhanced MRI (D) (arrows). The brachytherapy seeds also visible as signal void areas through all sequences (arrowheads). MRI/US fusion-guided biopsy confirmed recurrent prostate cancer.

Figure 27:

A 60-year-old patient with a prostate-specific antigen level of 0.2 ng/mL with a history of radical prostatectomy. Post-surgical MRI reveals that intravesical urine reaches the urethrovesical anastomosis, appearing hyperintense on T2-weighted axial (A), sagittal (B), and coronal (C) images (arrows). Additionally, the absence of diffusion restriction on high b-value diffusion-weighted imaging and the ADC map, coupled with no early enhancement on dynamic contrast-enhanced MRI, collectively suggest a stable post-operative state without signs of residual or recurrent cancer.

Figure 28:

A 62-year-old patient with a prostate-specific antigen (PSA) level of 0.23 ng/mL with a history of radical prostatectomy. There is a lesion in the 6–8 o’clock direction at the prostatectomy bed. The lesion appears hypointense on T2-weighted imaging (A), markedly hyperintense on high b–value diffusion-weighted imaging (B), hypointense on apparent diffusion coefficient (ADC) map and it has early contrast uptake on dynamic contrast-enhanced MRI (D). MRI/US fusion-guided biopsy of the lesion revealed recurrent prostate cancer.

Figure 29:

A 59-year-old patient with a prostate-specific antigen (PSA) level of 0.4 ng/mL with a history of radical prostatectomy. Following the lymph node dissection, the patient developed lymphoceles, which appear hyperintense on axial (A) and coronal (B) T2-weighted imaging (asterisks), hypointense on axial T1-weighted imaging (C) (arrow).

Figure 30:

A 74-year-old patient with a prostate-specific antigen level of 10.77 ng/mL with a history of focal laser ablation therapy. There is a lesion in the left apical-mid peripheral zone that appears isointense on T2-weighted imaging (A), hyperintense on high b-value diffusion-weighted imaging (B), hypointense on apparent diffusion coefficient (ADC) map with a focal early enhancement on dynamic contrast-enhanced MRI (D).

Figure 31:

A 74-year-old patient with a prostate-specific antigen level of 3.68 ng/mL with a history of cryotherapy. The left lateral aspect of the prostate appears markedly hypointense (asterisk) due to prior therapy. There are lesions located in the midline apical-base anterior transition zone (arrowheads) and in the midline to the left mid-base peripheral zone (arrows) both of which appear hypointense on T2-weighted imaging (A), hyperintensity on high b–value diffusion-weighted imaging (B), hypointensity on apparent diffusion coefficient (ADC) map and demonstrates early enhancement on dynamic contrast-enhanced MRI (D). Combined MRI/US fusion-guided and systematic biopsy revealed recurrent prostate cancer in both lesions.

Figure 32:

A 77-year-old patient with a prostate-specific antigen (PSA) level of 3.04 ng/mL with a history of high-intensity focused ultrasound (HIFU) ablation therapy. There is a soft tissue lesion in the 3 to 5 o’clock direction which displays slight hypointesity on T2-weighted imaging (A), hyperintensity on high b–value diffusion-weighted imaging (B), hypointensity on apparent diffusion coefficient (ADC) map and displays early enhancement on dynamic contrast-enhanced MRI (D) (arrows). MRI/US fusion-guided biopsy revealed recurrent prostate cancer.

Figure 33:

A 72-year-old patient with a prostate-specific antigen level of 6.79 ng/mL presented with a lesion in the right base anterior transition zone, which exhibited hypointensity on axial T2-weighted imaging (T2WI) (A), hyperintensity on high b-value diffusion-weighted imaging (DWI) (B), hypointensity on apparent diffusion coefficient (ADC) map (C) and with early focal contrast uptake on dynamic contrast-enhanced (DCE) MRI (D) (arrows). Targeted biopsy revealed International Society of Urological Pathology Group 2 prostate adenocarcinoma which was treated with irreversible electroporation therapy. Post-treatment, the treatment site is well circumscribed with heterogeneous signal characteristics on T2WI (E), and displays heterogeneous diffusion restriction on high b-value DWI (F) and ADC map (G) (arrows). However, there is no early enhancement on DCE MRI. Post-treatment biopsy from the area was negative for prostate cancer.

Figure 34:

A 66-year-old patient with a prostate-specific antigen (PSA) level of 2.8 ng/mL who previously had a transurethral resection of the prostate (TURP) for benign prostatic hyperplasia. Post-TURP imaging shows hyperintense signals in areas on axial (A), sagittal (B), and coronal (C) T2WI, indicating fluid presence (arrows) where prostate tissue was resected.

Figure 35:

A 70-year-old patient with a prostate-specific antigen level of 5.8 ng/mL presented with benign prostatic hyperplasia nodules, which exhibited heterogeneous signal intensity on axial (A), sagittal (B), and coronal (C) T2-weighted imaging (T2WI) (arrows). Following a simple prostatectomy, the prostate volume reduced from 139 cc to 15 cc, accompanied by a decrease in the PSA level to 0.7 ng/mL.. Post-operative imaging demonstrated that the area previously occupied by the transition zone is now filled with urine, exhibiting hyperintense signal on axial (D), sagittal (E), and coronal (F) T2WIs (arrowheads).

Figure 36:

A 53-year-old patient with a prostate-specific antigen level of 3.5 ng/mL, with a history of UroLift^™ treatment for benign prostatic hyperplasia. The metallic implants (arrows) appear as hypointense linear structures along the course of prostatic urethra bilaterally on axial (A), sagittal (B), and coronal (C) T2-weighted imaging. These implants could cause artifacts particularly on high b-value diffusion-weighted imaging (D) and apparent diffusion coefficient (ADC) map (E), however, the artifacts on dynamic contrast-enhanced MRI (F) are less prominent (arrowhead).

Figure 37:

A 64-year-old patient with a prostate-specific antigen level of 6.4 ng/mL, with a history of Rezum^™ treatment for benign prostatic hyperplasia. Treatment-associated cystic changes (arrows) are visible on the axial (A), sagittal (B), coronal (C) T2-weighted imaging, high b-value diffusion-weighted imaging (D), apparent diffusion coefficient (ADC) map (E), and dynamic contrast-enhanced MRI (F).

Figure 38:

A 71-year-old patient with a prostate-specific antigen level of 10.6 ng/mL, who presented with multiple benign prostatic hyperplasia (BPH) nodules. The nodules are characterized by their heterogeneous signal intensity accompanied by a hypointense capsules on axial (A) and sagittal (B) T2-weighted imaging (arrows). Some BPH nodules may display diffusion restriction, appearing hyperintense on high b-value diffusion-weighted imaging (C) and hypointense on apparent diffusion coefficient (ADC) map (D) (arrows). Following the prostate artery embolization for BPH treatment, the gland size decreased from 332 cc to 162 cc. The impacted left transition zone appears diffusely hypointense on axial (E) and sagittal (F) T2-weighted imaging (arrowhead). The diffusion restriction observed in some BPH nodules prior to the treatment is no longer visible on high b-value diffusion-weighted imaging (G) and ADC map (H).

Figure 39:

A 56-year-old patient with a prostate-specific antigen level of 3.9 ng/mL, who presented with a Prostate Imaging Reporting & Data System category 5 lesion in the left apical-mid peripheral zone. This lesion displayed a hypointense signal on T2-weighted imaging (A) and showed early contrast enhancement (B) (arrows). The presence of artifacts associated with rectal air (asterisk) visible on the sagittal T2-weighted imaging (C) hindered the interpretation of the high b-value diffusion-weighted imaging (D) and the apparent diffusion coefficient (ADC) map (E). MRI/US fusion-guided biopsy of the lesion revealed International Society of Urological Pathology group 2 prostate adenocarcinoma.

Figure 40:

A 61-year-old patient with a prostate-specific antigen level of 7.6 ng/mL, who presented with a Prostate Imaging Reporting & Data System category 3 lesion in the midline to left apical transition zone. This lesion was characterized by a slight hypointense signal on T2-weighted imaging (A), hyperintense signal on high b-value diffusion-weighted imaging (B) and slight hypointense signal on the apparent diffusion coefficient (ADC) map (C) (arrows). A deep learning-based AI algorithm (D) successfully identified this lesion (arrow). Subsequent MRI/US fusion-guided biopsy of this lesion confirmed the presence of International Society of Urological Pathology group 2 prostate adenocarcinoma.