Müllerian duct cyst is a congenital cystic lesion developing from incomplete regression of the Müllerian (paramesonephric) duct. In males, the Müllerian duct normally regresses during fetal development under the effect of anti-Müllerian hormone (AMH); if this regression is incomplete, a cystic lesion forms as a remnant structure proximal to the prostatic utricle. The Müllerian duct cyst is midline, starts from verumontanum level, and extends ABOVE the prostate — this feature is the key distinguishing criterion from utricle cyst. It may be pear or teardrop-shaped. Usually asymptomatic and discovered incidentally on mpMRI. In PI-RADS v2.1, it is considered a benign finding.
Age Range
20-40
Peak Age
30
Gender
Male predominant
Prevalence
Rare
In the male embryo, anti-Müllerian hormone (AMH) secreted by the testes causes regression of the Müllerian (paramesonephric) duct through apoptosis. This duct forms the uterus, fallopian tubes, and upper vagina in females; in males, it normally leaves only a small remnant as the prostatic utricle (utriculus prostaticus). When AMH effect is insufficient or regression is incomplete, the Müllerian duct remnant persists as a midline cystic structure behind the prostate. The cyst is lined by Müllerian epithelium (columnar or pseudostratified epithelium) — does NOT contain spermatozoa (unlike utricle cyst, it has no connection with the ejaculatory duct). Cyst fluid is clear serous or mildly proteinaceous. On imaging, it appears T2 hyperintense because the content is pure fluid. Absence of enhancement results from lack of vascularization beneath the epithelial lining. The extension above the prostate reflects the craniocaudal course of the Müllerian duct.
The most distinguishing feature of Müllerian duct cyst is its extension above the prostate. On sagittal T2-weighted images, the cyst clearly extends from verumontanum level beyond the superior border of the prostate cranially. This feature definitively differentiates from utricle cyst (which remains within the prostate and does not extend above). The embryological craniocaudal course of the Müllerian duct explains this extension pattern — the cyst follows the full course of the Müllerian duct remnant.
On T2-weighted images, markedly hyperintense cystic lesion at midline, posterior to prostate. Starts from verumontanum level and extends above the superior border of the prostate. Pear or teardrop-shaped morphology — base is wide (at verumontanum level), apex is narrow (supraprostatic). Thin wall, homogeneous fluid content, no septa or solid component.
Report Sentence
Midline T2 hyperintense cystic lesion posterior to prostate, starting from verumontanum level and extending above the prostate, consistent with Müllerian duct cyst.
Usually hypointense (water signal) on T1-weighted images. May be mildly hyperintense with proteinaceous content. T1 signal reflects the nature of cyst content — simple serous fluid gives low signal, proteinaceous/hemorrhagic fluid gives high signal.
Report Sentence
Midline cystic lesion showing hypointense signal on T1-weighted images, consistent with simple fluid content.
No enhancement on contrast-enhanced sequences. Thin wall may show minimal enhancement but no solid component or nodular enhancement is present. This feature supports benignity and differentiates from solid tumors.
Report Sentence
Non-enhancing midline prostatic cyst on contrast-enhanced sequences, consistent with Müllerian duct cyst.
No diffusion restriction on diffusion-weighted images — high signal on ADC map (free diffusion). This finding confirms simple fluid content and excludes infection/abscess possibility.
Report Sentence
Midline prostatic cyst showing no diffusion restriction, consistent with simple cystic structure.
On TRUS, anechoic or hypoechoic cystic lesion at midline in posterior prostate. Posterior acoustic enhancement is observed. Extension above prostate is evaluated with TRUS but not as reliable as MRI — cranial extension is better visualized with transabdominal US or MRI.
Report Sentence
Anechoic cystic lesion at midline in posterior prostate on TRUS, consistent with midline prostatic cyst; cranial extension should be evaluated with MRI.
On CT, well-defined, non-enhancing cystic lesion at water density (0-20 HU) at midline posterior to prostate. Large cysts can be detected on CT but small cysts may be missed due to CT's limited soft tissue contrast. CT provides initial evaluation in pelvic cyst differential but MRI is required for definitive diagnosis and morphological detail.
Report Sentence
Cystic lesion at water density at midline posterior to prostate on CT; MRI is recommended for definitive characterization.
Criteria
Size <2 cm, asymptomatic, incidental finding. Shows minimal extension above prostate. No follow-up or treatment required.
Distinct Features
Small size, minimal supraprostatic extension, no clinical significance
Criteria
Size >3-4 cm, may compress bladder neck or rectum. Urinary obstruction, dysuria, perineal pain. Surgical excision (transurethral or open) may be needed.
Distinct Features
Large size, compression symptoms, surgical indication, prominent supraprostatic extension
Criteria
Cyst infection — fever, pelvic pain, leukocytosis. On MRI, cyst wall thickening and enhancement, diffusion restriction, surrounding tissue edema. Intravenous antibiotics + drainage required.
Distinct Features
Wall thickening, diffusion restriction, surrounding edema, clinical infection signs
Distinguishing Feature
Utricle cyst is midline BUT does NOT extend above the prostate — remains within the prostate and is usually <10-15 mm in size. Müllerian duct cyst extends above the prostate and may be larger. Utricle cyst may contain spermatozoa (connected to ejaculatory duct), Müllerian duct cyst does not. Extension difference on sagittal T2 MRI is the definitive distinguishing criterion.
Distinguishing Feature
Seminal vesicle cyst is LATERALLY located and follows seminal vesicle anatomy. Müllerian duct cyst is MIDLINE. In seminal vesicle cyst, ipsilateral renal agenesis should be investigated (Zinner syndrome). Location difference (lateral vs midline) is easily differentiated on T2 axial MRI.
Distinguishing Feature
Prostatic retention cysts are usually small (<5 mm), intraprostatic, and associated with BPH. Müllerian duct cyst is larger, midline positioned, and extends above prostate. Retention cysts may be paramedian and scattered within prostate parenchyma.
Distinguishing Feature
Prostate abscess shows diffusion restriction, thick irregular enhancing wall, and surrounding tissue inflammation (edema). Müllerian duct cyst shows no diffusion restriction, characterized by thin smooth wall and absence of surrounding reaction. Abscess clinically presents with fever, pelvic pain, and leukocytosis.
Urgency
routineManagement
conservativeBiopsy
Not NeededFollow-up
no-follow-upAsymptomatic Müllerian duct cysts are benign findings requiring no treatment or follow-up. In PI-RADS v2.1, they are considered benign findings — not affecting scoring in prostate cancer screening. Symptomatic large cysts (urinary obstruction, dysuria, perineal pain) may be treated with transurethral resection (TUR), laparoscopic excision, or aspiration. In mpMRI reports, midline location and extension above the prostate should be clearly stated, and differentiation from utricle cyst should be made. DWI and clinical correlation are needed if infection is suspected.
Mullerian duct cysts are usually asymptomatic and incidental. Large cysts may cause bladder outlet obstruction, hemospermia, or infertility. Rarely, malignant transformation within the cyst has been reported. Aspiration or surgical excision is performed for symptomatic cysts.