Type I endometrial carcinoma (endometrioid adenocarcinoma) is the most common endometrial malignancy, accounting for 80-85% of all endometrial cancers. Typically occurs in postmenopausal women (mean age 60-65), though premenopausal cases exist. Develops on a background of endometrial hyperplasia due to chronic estrogen stimulation. Obesity, nulliparity, early menarche, late menopause, tamoxifen use, and Lynch syndrome are risk factors. Prognosis is generally favorable; most cases are diagnosed at early stage (FIGO I-II). MRI remains the gold standard for assessing myometrial invasion depth. Endometrial thickness >4 mm in postmenopausal women is suspicious and warrants biopsy.
Age Range
50-75
Peak Age
62
Gender
Female predominant
Prevalence
Common
Type I endometrial carcinoma is an estrogen-dependent neoplasm that develops due to chronic unopposed estrogen exposure. Estrogen stimulates endometrial glandular cell proliferation; when not counterbalanced by progesterone, the sequence of hyperplasia without atypia → atypical hyperplasia → well-differentiated carcinoma develops. At the molecular level, PTEN loss (40-80%), microsatellite instability (20-30%), PIK3CA mutation, and KRAS mutation are characteristic. The tumor invades from the endometrial cavity into the myometrium — invasion depth (FIGO stage IA: <50% vs IB: >50%) is the most important prognostic determinant. MRI findings reflect this pathology: the normal endometrial-myometrial border (junctional zone) is seen as a T2-hypointense line; tumor invasion disrupts this boundary. Tumor tissue shows diffusion restriction on DWI due to cellular density — marked decrease in ADC values is observed. On contrast-enhanced MRI, the tumor enhances less than the myometrium (rich vascular bed of myometrium vs relatively low vascular density of tumor), which demonstrates the invasion boundary through the 'subendometrial enhancement' pattern. Endometrial thickening on US is the initial finding in postmenopausal women — while normal postmenopausal endometrium is <4 mm, carcinoma thickens and makes the endometrium heterogeneous.
Focal or complete disruption of the T2-hypointense junctional zone between endometrium and myometrium due to tumor invasion on T2-weighted MRI — the most reliable indicator of myometrial invasion depth and the basis of FIGO staging.
On T2-weighted MRI, the endometrial mass appears with intermediate-to-high signal intensity. The normal junctional zone (JZ) is seen as a T2-hypointense thin line between the endometrium and myometrium. When the tumor invades the myometrium, this hypointense line is disrupted or disappears — the most important finding for determining invasion depth. If the JZ is completely preserved, there is no invasion (stage IA, no myometrial invasion). Focal JZ disruption suggests superficial invasion (<50%), while complete JZ loss suggests deep invasion (>50%). Should be evaluated in sagittal and coronal planes.
Report Sentence
A mass with intermediate-to-high signal intensity is identified in the endometrial cavity on T2-weighted sequences with [preserved / focally disrupted / completely lost] junctional zone, consistent with FIGO stage [IA / IB].
On DWI, the endometrial mass shows markedly bright signal at high b-values (b=800-1000) with low signal on the ADC map. ADC values are generally <0.9 x 10-3 mm2/s (normal endometrium ~1.5 x 10-3 mm2/s). Diffusion restriction reflects the cellular density of the tumor and improves diagnostic accuracy. DWI also helps determine the myometrial invasion boundary — the contrast between restricted tumor tissue and non-restricted myometrium visualizes the invasion front. Higher-grade tumors show more pronounced diffusion restriction.
Report Sentence
Marked diffusion restriction is identified in the endometrial mass on DWI with low ADC values, indicating high cellularity consistent with endometrial carcinoma.
On dynamic contrast-enhanced MRI, the tumor enhances less than the myometrium — particularly in the delayed phase (90-120 seconds) when the myometrium enhances intensely while the tumor remains relatively hypointense. This 'subendometrial enhancement' pattern is the most useful contrast sequence for determining the myometrial invasion boundary. In the early arterial phase, tumor and myometrium may show similar enhancement; however, the intense myometrial enhancement in the delayed phase clarifies the tumor boundary. Cervical stromal invasion is evaluated with the same principle — loss of enhancement in the cervical stroma indicates invasion.
Report Sentence
On delayed-phase contrast-enhanced MRI, the myometrium shows intense enhancement while the endometrial mass remains relatively hypointense; the subendometrial enhancement pattern demonstrates the myometrial invasion boundary.
Transvaginal US shows endometrial thickening (>4 mm in postmenopausal women, >15 mm in premenopausal women). The endometrium shows heterogeneous echogenicity — hyperechoic and hypoechoic areas may coexist. The endometrial-myometrial border may be regular or irregular. Fluid accumulation in the endometrial cavity (hematometra/pyometra) may be present. Color Doppler shows increased vascular flow in the endometrial mass — low resistance index (RI <0.40) is a finding favoring malignancy. US is the first-line screening method but is limited compared to MRI in determining myometrial invasion depth.
Report Sentence
Endometrial thickness measures [X] mm on transvaginal US with heterogeneous echogenicity; increased vascular flow is noted on Doppler examination. Pelvic MRI is recommended for evaluation of myometrial invasion depth.
Contrast-enhanced CT shows a hypodense or heterogeneously enhancing endometrial mass in the uterine cavity. The myometrium may be thinner than normal — asymmetric decrease in myometrial thickness is seen in the presence of invasion. Cervical invasion, parametrial extension, lymph node metastasis, and distant metastasis (lung, liver) are evaluated. CT is limited compared to MRI in determining myometrial invasion depth but is valuable for staging in advanced disease. The contrast difference between tumor and myometrium may increase in the delayed phase.
Report Sentence
A heterogeneously enhancing endometrial mass is identified in the uterine cavity on contrast-enhanced CT. Pelvic MRI is recommended for definitive assessment of myometrial invasion depth.
On T1-weighted sequences, endometrial carcinoma is generally isointense to the myometrium — T1 alone cannot differentiate tumor from normal tissue. However, T1 is valuable for hemorrhage detection: intratumoral hemorrhage or hematometra shows hyperintense signal on T1. Fat-suppressed T1 sequences better demonstrate enhancing tissue. Pre-contrast T1 imaging provides baseline images for post-contrast comparison.
Report Sentence
The endometrial mass is isointense to the myometrium on T1-weighted sequences; no intratumoral hemorrhage is detected.
FDG PET-CT shows increased FDG uptake in endometrial carcinoma — SUVmax is generally between 5-20. FDG uptake reflects the metabolic activity of the tumor and correlates with grade (higher SUVmax in higher-grade tumors). PET-CT is not routinely used in primary tumor staging but is valuable in detecting lymph node metastasis, peritoneal spread, and distant metastases in advanced disease. It plays an important role in recurrence detection and treatment response evaluation.
Report Sentence
Increased metabolic activity is identified in the endometrial mass on FDG PET-CT (SUVmax: [X]); lymph node or distant metastasis [is / is not] detected.
Criteria
Tumor confined to endometrium or invading inner half of myometrium — JZ preserved or focally disrupted. On MRI, tumor has not reached outer half of myometrium. Surgical pathology shows invasion depth <50% of myometrial thickness.
Distinct Features
JZ preserved or focally disrupted, outer half of myometrium intact, best prognosis group (>90% 5-year survival), surgery alone usually sufficient.
Criteria
Tumor invading outer half of myometrium — JZ completely disrupted, tumor close to or at serosal level but not extending beyond. MRI shows tumor signal in outer half of myometrium. Deep invasion significantly increases risk of lymph node metastasis.
Distinct Features
JZ completely lost, outer half of myometrium involved, lymph node metastasis risk 20-40%, adjuvant therapy (radiotherapy ± chemotherapy) may be needed.
Criteria
Tumor has invaded the stromal tissue of the cervix but has not spread beyond the uterus. MRI shows disruption of the T2-hypointense stromal ring of the cervix. Cervical stromal invasion is more clearly seen on contrast-enhanced sequences.
Distinct Features
Cervical stromal ring disrupted, no spread beyond uterus, radical hysterectomy + lymph node dissection indicated, adjuvant therapy planned.
Criteria
Stage III: Local spread beyond uterus — IIIA (serosa/adnexa), IIIB (vaginal/parametrial), IIIC1 (pelvic LN), IIIC2 (para-aortic LN). Stage IV: IVA (bladder/rectal mucosal invasion), IVB (distant metastasis — peritoneal, lung, liver, bone). Staging with MRI and CT.
Distinct Features
Spread beyond uterus, surgery + adjuvant chemoradiotherapy, systemic therapy, multidisciplinary approach, prognosis worsens proportionally with stage.
Distinguishing Feature
Type II (serous/clear cell) is more aggressive — usually shows deep myometrial invasion and peritoneal spread, can arise from thin endometrium (on a background of atrophy), more common in older age group.
Distinguishing Feature
Endometrial hyperplasia shows no myometrial invasion — JZ is completely preserved, no or minimal restriction on DWI, endometrial thickening is diffuse without mass formation.
Distinguishing Feature
Endometrial polyp appears as a well-defined, pedunculated mass — no restriction on DWI, intact JZ, generally isointense or slightly hypointense to endometrium on T2, fibrous core may appear hypointense on T2.
Distinguishing Feature
Submucosal leiomyoma shows homogeneous hypointense signal on T2 (carcinoma shows intermediate-to-high signal), no restriction on DWI (except in degeneration), well-defined and pushes but does not disrupt JZ.
Urgency
urgentManagement
surgicalBiopsy
NeededFollow-up
specialist-referralEndometrial biopsy (pipelle or hysteroscopic) is mandatory for diagnosis. Staging is performed with pelvic MRI — myometrial invasion depth, cervical invasion, and lymph node status are evaluated. Standard treatment is total hysterectomy + bilateral salpingo-oophorectomy + lymph node dissection/sentinel lymph node biopsy. FIGO stage IB and above requires adjuvant radiotherapy ± chemotherapy. Lynch syndrome screening (immunohistochemistry or MSI testing) should be performed in all cases. Early-stage (IA, grade 1-2) prognosis is excellent (>95% survival).
Type I endometrial carcinoma is the most common gynecological malignancy. Postmenopausal bleeding is the most common presenting symptom. MRI assessment of myometrial invasion depth and cervical extension is critical for surgical planning. Early stage (Stage I) has >90% 5-year survival. Treatment is usually total hysterectomy with bilateral salpingo-oophorectomy.