Submucosal leiomyoma is a type of leiomyoma originating from the myometrium and growing toward the endometrial cavity. Although it constitutes only 5-10% of all fibroids, it is the most symptomatic type — most strongly associated with abnormal uterine bleeding (menorrhagia, metrorrhagia) and infertility. In FIGO classification, it is subclassified as Type 0 (pedunculated, entirely intracavitary), Type 1 (<50% intramural), and Type 2 (≥50% intramural). This classification is critical in treatment planning: Type 0 and Type 1 are suitable for hysteroscopic resection, while Type 2 may require laparoscopic/laparotomic approach. Saline infusion sonohysterography (SIS/SHG) is the gold standard US method for evaluating submucosal fibroids — precisely determines the amount of intracavitary component. MRI is the most valuable modality for mapping in multiple fibroids and FIGO typing. On US, it appears as a hypoechoic mass deforming or invading the endometrial cavity.
Age Range
30-55
Peak Age
42
Gender
Female predominant
Prevalence
Common
Submucosal leiomyoma originates from the subendometrial region of the myometrium and grows toward the endometrial cavity. Its pathophysiology is identical to intramural leiomyoma (smooth muscle monoclonal proliferation, MED12 mutation, estrogen/progesterone-dependent growth), but its anatomic location determines clinical impact. Growth toward the endometrial cavity causes symptoms through several critical mechanisms: (1) Increases endometrial surface area → increased menstrual bleeding volume (menorrhagia), (2) Disrupts endometrial vascular architecture — venous plexuses around submucosal fibroids are compressed or dilated → irregular bleeding (metrorrhagia), (3) Cavity distortion prevents embryo implantation → infertility or recurrent miscarriage, (4) Large pedunculated fibroids may prolapse through the cervical canal → cervical dilation and acute pain. On imaging, the relationship with the endometrial cavity is key to diagnosis: on US, a hypoechoic mass distorting/deforming the endometrial stripe; on SIS, the intracavitary component is visualized surrounded by saline. On MR T2, the hypointense mass contrasts with hyperintense endometrial fluid/tissue → cavity relationship is clearly assessed. FIGO subclassification is based on intramural depth of the fibroid and directly determines treatment choice.
Hypoechoic intracavitary mass surrounded by saline fluid infused into the endometrial cavity on saline infusion sonohysterography (SIS) — gold standard method for diagnosis and FIGO classification (Type 0/1/2) of submucosal myoma. Intracavitary component amount is directly measured for treatment planning.
Hypoechoic solid mass deforming or protruding into the endometrial cavity. The endometrial stripe (echogenic line) appears thinned or disrupted over the lesion. In pedunculated (Type 0) lesions, the mass is entirely intracavitary connected to the myometrium by a narrow stalk. In Type 1-2, it continues with a broad base within the myometrium. Cystic degeneration or calcification may be seen. Transvaginal US is superior to transabdominal US — high-frequency probe provides more detailed endometrial cavity evaluation.
Report Sentence
A ___ x ___ mm hypoechoic solid mass protruding into the endometrial cavity is seen, consistent with submucosal leiomyoma; intracavitary component is estimated at approximately ___%.
Feeding vessel detected at myometrium-myoma junction (stalk region) on Doppler. In pedunculated (Type 0) lesions, a single feeding artery is traced from the stalk — important clue for differentiation from endometrial polyp. Peripheral circumferential vascularity may be seen as in intramural leiomyomas. Vascularity of intracavitary component shows myometrium-based feeding pattern — different from endometrial-origin lesions.
Report Sentence
A feeding vascular structure originating from the myometrium is observed at the stalk region of the intracavitary mass on color Doppler.
SIS (saline infusion sonohysterography): after sterile saline infusion into the cavity, the intracavitary mass is surrounded by saline fluid and clearly visualized. Intracavitary and intramural components of the lesion are precisely measured → FIGO classification is made: Type 0 = entirely intracavitary, Type 1 = ≤50% intramural, Type 2 = >50% intramural. The surface of the intracavitary mass in SIS is smooth and covered with endometrium. SIS is superior for differentiation from polyp — polyp is usually echogenic, myoma is hypoechoic.
Report Sentence
On SIS, a ___ x ___ mm hypoechoic intracavitary mass surrounded by saline fluid is seen in the endometrial cavity with intracavitary component estimated at ___% (FIGO Type ___).
Hypointense mass protruding into the endometrial cavity on T2W — creates marked contrast with surrounding hyperintense endometrium and cavity fluid. Pseudocapsule appears as a thin hyperintense ring on the myometrial side. Intracavitary component ratio and intramural depth are best evaluated on T2 → FIGO typing is performed. Junctional zone (inner myometrium, T2 hypointense) relationship with lesion is evaluated — submucosal myoma disrupts or thins the junctional zone. T2 sequence is the gold standard for mapping multiple fibroids.
Report Sentence
A ___ x ___ mm hypointense mass protruding into the endometrial cavity is seen on T2W with intracavitary component ratio of ___%, consistent with FIGO Type ___ submucosal leiomyoma.
Mass isointense or slightly hypointense to myometrium on T1W. Endometrial cavity relationship is not as clear on T1 as on T2 — cavity fluid and endometrium show low signal on T1, myoma also shows low signal → poor contrast. T1 hyperintensity in hemorrhagic degeneration. Contrast-enhanced T1 sequences help in submucosal myoma-endometrium differentiation — endometrium enhances more prominently than myoma.
Report Sentence
The lesion protruding into the endometrial cavity shows signal isointense to the myometrium on T1W.
Submucosal leiomyoma does not show significant diffusion restriction on DWI — ADC values are normal or mildly reduced. This finding is critical for differentiation from endometrial carcinoma and leiomyosarcoma: marked restriction and low ADC are expected in endometrial carcinoma. Cavity fluid shows low signal on DWI and high signal on ADC → creates contrast with myoma.
Report Sentence
No significant diffusion restriction is detected in the submucosal lesion on DWI/ADC map; no findings consistent with malignant lesion.
Criteria
Mass entirely within endometrial cavity, connected to myometrium by narrow stalk, no intramural component
Distinct Features
Most suitable type for hysteroscopic resection. Single feeding artery traced from stalk. May prolapse through cervical canal. SIS + Doppler combination critical for differentiation from endometrial polyp.
Criteria
Intracavitary component >50%, intramural component ≤50%
Distinct Features
Generally suitable for hysteroscopic resection — can be completed in single session by experienced surgeon. Large intracavitary component surrounded by saline and small base within myometrium on SIS. Cavity relationship clear on MR T2.
Criteria
Intramural component >50%, intracavitary component ≤50%
Distinct Features
Hysteroscopic resection challenging — two-session approach or laparoscopic/laparotomic myomectomy may be needed. Large component within myometrium on SIS, small protrusion into cavity. May be confused with intramural myoma — cavity relationship should be confirmed with SIS and MRI.
Distinguishing Feature
Endometrial polyp shows isoechoic/hyperechoic intracavitary mass, feeding artery originates from endometrial basal layer (not myometrium). Polyp is echogenic on SIS, myoma is hypoechoic. Cystic areas (dilated glands) common in polyp. Polyp shows intermediate signal on MR T2, myoma is markedly hypointense.
Distinguishing Feature
Endometrial carcinoma shows intermediate-high T2 signal, marked diffusion restriction (low ADC), junctional zone invasion/disruption, irregular enhancement. Submucosal myoma shows T2 hypointense, no DWI restriction, junctional zone displaced but not invaded, smooth borders.
Distinguishing Feature
In intramural leiomyoma, mass is entirely within myometrium, endometrial cavity is intact/not deformed. No lesion demonstrated within cavity on SIS. T2 hypointense mass located in mid-myometrium, does not displace endometrial stripe.
Distinguishing Feature
Endometrial hyperplasia shows diffuse endometrial thickening (not focal mass), no intracavitary mass on SIS but thickened endometrium does not thin with saline. Submucosal myoma shows focal mass, hypoechoic lesion surrounded by saline on SIS.
Urgency
routineManagement
surgicalBiopsy
Not NeededFollow-up
6-monthSubmucosal leiomyoma is the most symptomatic fibroid type: menorrhagia (30% require transfusion), infertility (50-70% improvement after hysteroscopy), recurrent miscarriage. FIGO Type 0 and 1 are suitable for hysteroscopic myomectomy — minimally invasive, fertility preserving, low morbidity. Type 2 hysteroscopic resection is challenging, laparoscopic/open myomectomy or two-session hysteroscopy may be needed. Pre-op SIS or MRI with FIGO typing is mandatory in treatment planning. GnRH agonists may be used for pre-op fibroid shrinkage and anemia correction. UAE may be contraindicated in submucosal fibroids (necrotic tissue may expulse into cavity). MRgFUS may be applied in suitable cases. New postmenopausal submucosal mass must be differentiated from endometrial carcinoma — biopsy required.
Submucosal leiomyomas are one of the most common uterine causes of menorrhagia, anemia, and infertility. Hysteroscopic myomectomy is the primary treatment (FIGO Type 0-1). Hysteroscopic resection is more complex for Type 2 myomas. Fertility-preserving surgical planning is best evaluated with MRI.