Impact of FIGO 2023 Staging on MRI Evaluation of Endometrial Cancer: Highlighted Version

Abstract

The 2023 revision of the International Federation of Gynecology and Obstetrics (FIGO) staging system for endometrial carcinoma (EC) has introduced significant updates, including refined anatomic definitions and the incorporation of molecular subtypes such as POLE mutations, mismatch repair deficiency, and p53 abnormalities. Magnetic resonance imaging (MRI) remains the preferred modality for preoperative staging of EC due to its superior soft tissue contrast and functional imaging capabilities. This review discusses the technical considerations for MRI acquisition, with particular emphasis on the impact of the revised staging system on imaging interpretation. It highlights the role of MRI in evaluating eligibility for fertility-sparing treatments and in posttreatment surveillance. Radiologists must be familiar with these changes to ensure accurate staging and optimal patient management. Lastly, it elucidates the utility of imaging biomarkers such as apparent diffusion coefficient values, tumor size, and patterns of spread as potential surrogates for histologic and molecular classification. Integrating molecular profiling with MRI interpretation represents a critical advancement toward risk-adapted therapeutic strategies in endometrial cancer.

Keywords

endometrial carcinoma - FIGO 2023 staging - magnetic resonance imaging (MRI) - molecular classification - radiogenomics

Introduction

Endometrial carcinoma (EC) is the most common gynecologic malignancy in many regions, and its incidence continues to rise globally.[1] [2] [3] The staging system proposed by the International Federation of Gynecology and Obstetrics (FIGO) is the gold standard for staging of EC. Recent updates (2023) have been driven by the need for a more precise prognostic classification that incorporates molecular profiles (POLE mutations, mismatch repair status, p53 abnormalities) alongside traditional histopathological features such as lymphovascular space invasion (LVSI), myometrial invasion depth, and cervical stromal involvement.[4] These changes accurately reflect tumor biology and prognosis, especially in high-risk patients.

Although magnetic resonance imaging (MRI) is not formally included in the FIGO staging system, it remains the preferred imaging modality for preoperative assessment. Current guidelines from the American College of Radiology and the European Society of Urogenital Radiology endorse MRI as the modality of choice for treatment planning.[5] [6] MRI helps in the assessment of myometrial invasion, cervical stromal involvement, and adnexal or nodal disease. It is useful in evaluating eligibility for fertility-sparing options or nonsurgical management, as well as monitoring therapy response in patients undergoing chemoradiation or hormonal therapy.[1]

While the revised FIGO 2023 system has been shown to improve prognostication and potentially guide more personalized treatment strategies, its impact on imaging interpretation, diagnostic workflow, and radiologic reporting has not been fully elucidated. This review article aims to educate radiologists on the evolving landscape of endometrial cancer staging. It highlights how these changes affect MRI interpretation and reporting. By integrating molecular insights with traditional imaging findings, clinicians can better stratify patient risk, personalize treatment, and avoid unnecessary interventions.

Histopathology and Molecular Subtypes

Conventionally, EC is classified into two types: type I (estrogen-dependent, low-grade endometrioid) with a favorable prognosis, and type II (nonestrogen-dependent, high-grade endometrioid, serous, and clear cell) with aggressive behavior and poorer outcomes due to a higher risk of spread.[4] [7] [8] The 5th edition of the World Health Organization Classification of Tumors of the Female Genital Tract, however, classifies EC into several distinct histological types, each with specific morphologic features, natural history, and clinical behavior.[9] In the revised FIGO staging, these histological types are broadly categorized into nonaggressive and aggressive types ([Table 1]). Nonaggressive type includes low-grade endometrioid ECs (EECs), while the aggressive type includes high-grade EECs and all other histological subtypes.

Table 1 FIGO 2023 histopathology subtypes

Subtypes	Included tumors	Prognostic significance
Nonaggressive	Low-grade endometrioid carcinomas	Generally favorable prognosis; staging depends on depth of invasion and LVSI
Aggressive	High-grade endometrioid, serous, clear cell, undifferentiated, carcinosarcoma, mesonephric-like, mixed, GI-type mucinous	Higher risk of LVSI, nodal spread, and poorer outcomes; classified as IC or IIC regardless of invasion depth

Abbreviations: FIGO, International Federation of Gynecology and Obstetrics; GI, gastrointestinal; LVSI, lymphovascular space invasion.

The high-grade ECs (grade 3) are now recognized as a clinically and molecularly heterogeneous group.[4] Molecular classification plays a vital role in prognostication and treatment planning for these tumors ([Table 2]).

Table 2 Molecular subgroups of high-grade endometrial carcinoma and their prognostic implications

Molecular subgroup	Key features	Prognosis
POLE-mutated (POLEmut)	Ultra-mutated tumors with distinctive molecular signature	Excellent, even in high-grade or early-stage disease
p53-abnormal (p53abn)	Reflects serous-like biology; TP53 mutation or aberrant immunostaining	Poor, associated with aggressive behavior
Mismatch repair-deficient (MMRd)	Loss of MMR protein expression; MSI-high	Intermediate; histologic grade less predictive of outcome
NSMP (no specific molecular profile)	Lack of POLE, p53, or MMR abnormalities; wide morphologic spectrum	Variable; ER-negative NSMP shows worse prognosis

Abbreviations: ER, estrogen receptor; MSI, microsatellite instability.

MRI Technique

The recommended MRI protocol ([Table 3]) for endometrial cancer remains unchanged in the FIGO 2023 guidelines and continues to rely on a multiparametric approach using at least a 1.5-T system with a multichannel phased-array surface coil. High-resolution T2-weighted (T2W) imaging is performed in sagittal, coronal, and axial-oblique planes, with a small field of view and thin sections (3–4 mm) for optimal assessment of myometrial invasion ([Fig. 1A, B]). Diffusion-weighted imaging (DWI) is acquired in one or two planes using low b-values around 50 sec/mm² and high b-values between 800 and 1000 sec/mm², allowing reliable tumor detection and characterization. Dynamic contrast-enhanced (DCE) MRI is obtained in standardized phases, including early phase at 30 to 40 seconds, equilibrium phase at 120 to 180 seconds, and delayed phase acquisition at 4 to 5 minutes ([Fig. 1C–E]). Additional axial T2W sequences, with or without DWI, covering the renal hila to the pubic symphysis can assist in evaluating nodal and skeletal involvement. Depending on specific clinical requirements, such as fertility preservation, either multiphasic DCE-MRI or high-resolution single-phase imaging may be selected at the radiologist's discretion.

Table 3 Recommended MRI protocol in suspected cases of endometrial carcinoma

Parameter	Recommended setting
Magnet strength	≥ 1.5 T
Coil	Multichannel phased-array
Position	Supine
FOV	Small pelvic FOV for uterus; large FOV from renal hila to pubic symphysis for nodal assessment
Section thickness	3–4 mm for high-resolution pelvic sequences
Key sequences	T2-weighted (sagittal, axial oblique, coronal)
	DWI (b≈50 and 800–1000 s/mm2)
	ADC map
	DCE-MRI: Early phase (30–40 s postcontrast); Equilibrium phase (120–180 s postcontrast); Delayed phase (4–5 min postcontrast)
Patient preparation	Void before scan
	Consider 4–6 h fasting
	Optional antispasmodic agent
	Optional vaginal gel (30–60 mL)

Abbreviations: ADC, apparent diffusion coefficient; DCE, dynamic contrast-enhanced; DWI, diffusion-weighted imaging; FOV, field of view; MRI, magnetic resonance imaging.

Fig. 1 Magnetic resonance imaging (MRI) protocol for endometrial cancer. (A) Sagittal T2-weighted (T2W) image demonstrating the plane of acquisition of oblique axial images. (B) Sagittal T2W image demonstrating the plane of acquisition of coronal images. Dynamic contrast-enhanced sagittal T1 fat-saturated (FS) images (C) precontrast and (D) early phase (30–60 seconds postcontrast) demonstrating subendometrial enhancement (white arrow) and enhancement of cervical mucosa (white arrowhead). (E) Equilibrium phase (120–180 seconds postcontrast) demonstrating myometrial enhancement (black arrow) and early cervical stromal enhancement (black arrowhead).

Imaging Findings

Normal Anatomy

A thorough understanding of normal pelvic anatomy is essential for accurate interpretation of disease extent. On T2W MRI, the uterus displays a trilaminar zonal anatomy: a central high-signal endometrium, a low-signal junctional zone/inner myometrium, and an intermediate-signal outer myometrium. The inner myometrium continues caudally as a fibrous part of the cervical stroma, while rest of the myometrium continues as outer interstitial cervical stroma ([Fig. 2A]). Post menopause, delineation of the junctional zone becomes difficult due to endometrial and myometrial atrophy, leading to poor assessment of tumor invasion ([Fig. 2B]).

Fig. 2 (A) Sagittal T2-weighted (T2W) image in a premenopausal woman depicting the normal trilaminar zonal anatomy: a central high-signal endometrium (white arrow), a low-signal junctional zone/inner myometrium (white arrowhead), and an intermediate-signal outer myometrium (black arrow). The uterine serosa appears a continuous hypointense line surrounding the myometrium (black arrowhead). (B) Sagittal T2W image in a postmenopausal woman depicting the loss of zonal anatomy.

DWI enhances tumor detection and helps in assessing the depth of invasion of the myometrium and cervical stroma. EC typically demonstrates high signal on high b-value DWI with corresponding low apparent diffusion coefficient (ADC) values, allowing clearer delineation of myometrial and cervical stromal invasion. DWI is especially helpful in identifying lesions that are poorly demarcated on T2W or contrast-enhanced (CE) sequences, such as those isointense to the myometrium or those that are obscured by coexisting pathologies (adenomyosis). It is also imperative in patients with distorted zonal anatomy, such as postmenopausal women.

DCE-MRI adds further specificity. In the early phase images, preservation of a smooth, continuous subendometrial enhancement line effectively excludes myometrial invasion ([Fig. 1D]), while the equilibrium phase is most reliable for evaluating the depth of myometrial involvement because the contrast between enhanced myometrium and unenhanced tumor is maximum during this time ([Fig. 1E]). Delayed phase images are preferred for assessing cervical stromal invasion as cervical stroma starts enhancing and the tumor starts to wash out.

FIGO 2023 Revised Staging

Recent revisions to the FIGO staging system, along with their comparison to the 2009 version, are summarized in [Table 4].

Table 4 Comparison of the 2009 and 2023 FIGO staging systems

2009 FIGO staging system	2023 FIGO staging system
Stage I	Stage I
Tumor confined to uterine body	Stage based on histology (aggressive vs. nonaggressive), depth of invasion, and LVSI
IA and IB distinguished only by myometrial invasion: < 50% (IA) or ≥ 50% (IB)	IA and IB reserved for nonaggressive tumors without substantial LVSI; IA = < 50% invasion, IB = > 50% invasion
No separate category for tumors without myometrial invasion	Further subdivision for nonaggressive tumors: IA1: no invasion; IA2/IA3: < 50% invasion. IA3 includes synchronous ovarian involvement
No separate category for histologically aggressive tumors	Aggressive tumors: IC: no myometrial invasion; IIC: any myometrial invasion
Stage II	Stage II
Tumor limited to uterus with cervical stromal invasion	Defined by histologic type, presence of cervical stromal invasion, LVSI, and myometrial invasion
No separate categories for histologically aggressive and nonaggressive tumors	IIA: nonaggressive with cervical stromal invasion; IIB: nonaggressive with substantial LVSI; IIC: aggressive with any myometrial invasion
Stage III	Stage III
Extrauterine pelvic spread	Regional spread beyond uterus.
IIIA includes adnexal or serosal involvement. No separate category for synchronous involvement	IIIA1: adnexal spread (except synchronous involvement); IIIA2: uterine subserosal/serosal involvement
IIIB includes vaginal or parametrial involvement	IIIB1: vaginal/parametrial extension; IIIB2: pelvic peritoneal disease (shifted from stage IV in 2009)
IIIC1/IIIC2 distinguish pelvic vs. para-aortic nodes but do not separate micro- from macrometastases	Further stratified into micrometastases (IIIC1i, IIIC2i) and macrometastases (IIIC1ii, IIIC2ii)
Stage IV	Stage IV
IVA: bladder/rectal invasion. IVB: distant metastasis, including abdominal spread and inguinal nodes	IVA: bladder or bowel mucosal involvement. IVB: abdominal peritoneal metastasis. IVC: distant metastasis to extra- or intra-abdominal nodes or organs

Abbreviations: FIGO, International Federation of Gynecology and Obstetrics; LVSI, lymphovascular space invasion.

Stage I

The broad classification of stage I into IA (myometrial invasion < 50%) and IB (invasion ≥ 50%) has been modified by incorporating both histologic aggressiveness and LVSI status. Stage IA now includes nonaggressive tumors without significant LVSI (< 5 vessels involved) and is further subdivided: IA1 represents tumors with no myometrial invasion, IA2 for invasion of up to less than 50%, and IA3 includes tumors with less than 50% invasion and low-grade synchronous ovarian involvement. Stage IB remains reserved for those with more than 50% myometrial invasion. For aggressive histology, the classification shifts—stage IC includes tumors with no myometrial invasion, while stage IIC includes any degree of myometrial invasion.

Stage II

Previously used to categorize all tumors with cervical stromal invasion, stage II is now subdivided into three categories: stage IIA for nonaggressive tumors without substantial LVSI invading cervical stroma, stage IIB for nonaggressive tumors with substantial LVSI (≥ 5 vessels involved), and stage IIC for aggressive tumors invading the myometrium and/or the cervical stroma.

Stage III

Unlike stage I and II, histological aggressiveness does not dictate stage III subclassification, highlighting the diminished role of histopathology once the tumor spreads outside the uterus. Prognosis, then, is predominantly determined by the degree of anatomic spread. However, certain modifications have still been made. Stage IIIA denotes adnexal (IIIA1) involvement, except when it is synchronous (stage IA3), and serosal involvement (IIIA2). Stage IIIB encompasses vaginal or parametrial involvement (IIIB1) and pelvic peritoneal involvement (IIIB2). Downstaging of pelvic peritoneal metastases from stage IVB to IIIB acknowledges that outcomes for these patients are more aligned with advanced locoregional disease than with distant metastatic disease. Stage IIIC is subdivided into IIIC1 (metastasis to pelvic nodes) and IIIC2 (metastasis to para-aortic nodes) and is further subclassified into micrometastasis (lesions measuring 0.2–2 mm or containing over 200 cells) and macrometastasis (lesions larger than 2 mm).

Stage IV

Stage IVA remains largely unchanged and still refers to direct spread to the bowel or bladder mucosa. A newer subcategory, stage IVB, has been introduced to include abdominal peritoneal metastases. True distant metastases are now categorized under stage IVC (extra-abdominal lymph nodes or nodes superior to renal hilum, brain, bones, liver, or lungs).

Inclusion of Molecular Subtypes into FIGO Staging

In the revised FIGO system, the staging of EC primarily remains based on surgical and anatomical assessment for stage III and stage IV. However, if molecular classification is available, specific modifications are introduced in early-stage disease (I and II) to reflect prognostic implications more accurately.

FIGO stage I or II tumors exhibiting POLEmut or p53abn profiles are reclassified based on their molecular subtype into:

Stage IAm _POLEmut: Refers to a POLEmut EC confined to the uterus, with or without cervical involvement, and irrespective of histologic type or extent of LVSI.

Stage IICm _p53abn: Denotes a p53-abnormal carcinoma limited to the uterus, including cases with any depth of myometrial or cervical invasion, regardless of histologic type and LVSI status.

In contrast, mismatch repair deficiency (MMR)-deficient (MMRd) and NSMP (no specific molecular profile) tumors do not alter the anatomical FIGO stage in early disease but should still be documented for research and prognostic purposes.

Impact on Imaging Interpretation

The 2023 FIGO staging update integrates molecular profiling with revised anatomic criteria, necessitating refinements in MRI interpretation. Consequently, careful review of the biopsy and histologic findings before imaging assessment has become indispensable, as staging now relies not only on tumor extent but also on its underlying biology and molecular subtype. An algorithmic approach can be used for ease of interpretation ([Fig. 3]).

Fig. 3 Algorithmic approach to imaging interpretation based on the International Federation of Gynecology and Obstetrics (FIGO) 2023 modifications. (A) Metastases to extra- or intra-abdominal (above the renal hila) lymph nodes as well as metastases to the brain, lungs, liver, or bone. (B) Vaginal or parametrial involvement (IIIB1) and pelvic peritoneal involvement (IIIB2). (C) Criteria for synchronous adnexal involvement—(1) superficial myometrial invasion (< 50%), (2) no significant lymphovascular space invasion (LVSI), (3) no extraovarian metastases, and (4) unilateral ovarian lesion, confined within the ovary without capsular invasion or rupture (equivalent to pT1a). (D) Lymphovascular space invasion is considered significant when 5 or more vessels are involved.

Tumor Localized to the Endometrium

The tumor is said to be localized to the endometrium when the continuity of subendometrial enhancement (early postcontrast images) and junctional zone is intact ([Fig. 4]).[1] These tumors may present as focal/diffuse endometrial thickening or an endometrial polyp. When a tumor is localized to the endometrium, the next step is to assess the histological subtype. If the tumor is nonaggressive, it is categorized as stage IA1, while aggressive tumors are categorized into stage IC.

Fig. 4 Magnetic resonance imaging (MRI) findings in a patient with localized endometrial cancer. (A) Coronal T2-weighted (T2W) image demonstrating intact hypointense junctional zone (arrow) between the hyperintense endometrium and hypointense myometrium. A small fibroid (asterisk) is seen indenting onto the endometrium. (B) Diffusion-weighted image and (C) its corresponding apparent diffusion coefficient (ADC) map confirm noninvasion of the myometrium.

Myometrial Invasion

Accurate evaluation of myometrial invasion is essential for risk assessment and staging. Axial oblique and sagittal T2W sequences are best for assessment of depth of myometrial involvement, which is done by calculating the distance from the expected endomyometrial junction to the outer tumor margin and comparing it with the thickness of the adjacent myometrium. Deep invasion, defined as tumor extension beyond 50% of the myometrial thickness ([Fig. 5]), is strongly associated with higher grade of tumor, lymphovascular invasion, and nodal spread. Combining DWI with CE-MRI improves diagnostic clarity, especially in difficult cases involving adenomyosis, fibroids, or atrophic changes in the postmenopausal uterus. However, the presence of myometrial invasion does not necessarily mean stage I cancer according to the new guidelines. Once the degree of myometrial invasion has been assessed, tumor histopathology should be reviewed. A nonaggressive tumor without significant LVSI is categorized into IA2 if the depth of invasion is < 50% and into IB if the depth is > 50%. For aggressive tumors and nonaggressive tumors with significant LVSI, depth of invasion no longer dictates staging, and hence these are categorized into IIC and IIB, respectively.

Fig. 5 Endometrial cancer invading into the myometrium. (A) Sagittal T2-weighted (T2W) image shows loss of junctional zone continuity due to an iso-hypointense mass arising from the endometrium invading more than 50% of the adjacent myometrium (white arrow). (B) Postcontrast sagittal T1 fat-saturated (FS) image reveals invasion of > 50% of the myometrium by a relatively hypoenhancing tumor (white arrow). (C) Diffusion-weighted image and (D) its corresponding apparent diffusion coefficient (ADC) map reveal the presence of strong restriction within the mass (white arrows).

Cervical Stromal Invasion

MRI is also critical in identifying cervical stromal involvement, which is linked with poorer prognosis and may alter therapeutic strategies. Tumor infiltration appears as an interruption of the hypointense cervical stroma on T2W images and abnormal enhancement patterns on delayed CE-MRI ([Fig. 6]). DWI highlights high signal intensity in affected areas, corresponding to low signal on ADC maps. It is important to distinguish true invasion from mere tumor impingement on the cervical canal, which may mimic stromal involvement due to compression effects. Nonaggressive tumors without significant LVSI are staged IIA. Aggressive tumors, on the other hand, are staged IIC (same as aggressive tumors with myometrial invasion).

Fig. 6 Endometrial cancer with cervical stromal invasion. (A) Sagittal T2-weighted (T2W) image shows an iso-hypointense mass distending the endometrial cavity, invading the myometrium (yellow arrow), and infiltrating into the cervical stroma (arrow). Cervical stromal invasion is confirmed on (B) sagittal diffusion-weighted image and (C) postcontrast sagittal T1 fat-saturated (FS) image.

Adnexal Involvement

Determining whether adnexal abnormalities represent metastatic spread or synchronous primary ovarian tumors has a significant impact on current staging. According to guidelines, all of the following criteria must be met to differentiate low-grade endometrioid carcinoma with synchronous ovarian involvement (stage IA3) from metastatic spread (stage IIIA1): (1) superficial myometrial invasion (< 50%), (2) no significant LVSI, (3) no extraovarian metastases, and (4) unilateral ovarian lesion, confined within ovary without invasion or rupture of the capsule (equivalent to pT1a) ([Fig. 7]).

Fig. 7 Synchronous ovarian involvement. (A) Sagittal T2-weighted (T2W) image reveals an isointense mass distending the endometrial cavity and invading < 50% of the posterior myometrium (arrow). (B) Coronal T2W image shows a well-defined hypointense lesion (arrowhead) confined to the right ovary without any radiological evidence of capsular breach. (C) Axial-oblique diffusion-weighted image does not reveal any obvious restriction in the endometrial (arrow) or ovarian (arrowhead) lesion, a feature characteristic of low-grade tumors.

Fig. 8 Endometrial cancer with serosal and adnexal involvement. (A, B) Axial-oblique T2-weighted (T2W) images reveal an iso-hypointense mass arising from the endometrium, invading the myometrium, with a focal breach (arrowhead) in the T2-hypointense serosal rim. Tumor deposits (arrows) are noted in bilateral adnexa (International Federation of Gynecology and Obstetrics [FIGO] stage IIIA2). (C) Axial-oblique diffusion-weighted image shows restricted diffusion in the primary tumor (arrowhead) and its metastatic deposits (arrow).

Serosal and Subserosal Involvement

Extension of the tumor to the uterine serosa is indicated by contour irregularity and loss of the hypointense outer myometrial rim on T2W MRI, along with discontinuous peripheral enhancement ([Fig. 8]). Serosal/subserosal involvement is still categorized under stage IIIA, similar to the previous staging.

Vaginal and Parametrial Involvement

MRI can detect tumor spread to the vagina or parametrium either as direct contiguous growth or as separate metastatic foci. DWI and CE-MRI are valuable for evaluating small or ambiguous lesions. Accurate differentiation from benign inflammatory or reactive conditions is crucial, as vaginal or parametrial invasion corresponds to FIGO stage IIIB and warrants an altered management approach.

Lymph Node Assessment

Lymphatic spread is a major prognostic marker in endometrial cancer. Nodes larger than 8 mm (pelvis) or 10 mm (abdomen), those with round shape, heterogeneous signal, necrosis, or nodal clustering are considered suspicious. While MRI may miss microscopic metastases in normal-sized nodes, DWI can assist in identifying subtle abnormalities, although it is more useful for detection than characterization. Fluorodeoxyglucose positron emission tomography (PET)/ computed tomography (CT) or PET/MRI may be used to clarify equivocal findings. When suspicious lymph nodes are present, anatomic delineation of the involved group is important as current guidelines categorize suprarenal and inguinal lymph nodes as distant metastases (stage IVB).

Bladder and Bowel Involvement

Involvement of the bladder or rectum implies advanced disease (FIGO stage IVA). MRI findings include obliteration of the fat between the organ and the tumor, and a breach in the muscularis propria signal on T2 or postcontrast images ([Fig. 9]). True mucosal invasion may be indicated by an intraluminal tumor. Care must be taken to differentiate between tumor and benign bladder wall thickening, such as edema. When imaging is inconclusive, endoscopic evaluation is recommended.

Fig. 9 International Federation of Gynecology and Obstetrics (FIGO) stage IV endometrial cancers. Sagittal T2-weighted (T2W) image shows an isointense mass (asterisk) arising from and distending the endometrial cavity (arrow). The mass is seen invading the anterior myometrial wall, obliterating the fat plane between the bladder and uterus, and involving the bladder mucosa (arrowhead)—stage IVA.

Peritoneal Deposits

Dissemination to the peritoneum manifests as nodular implants or serosal plaques, often accompanied by ascites, especially in aggressive tumor subtypes. DWI improves the detection of small or subtle implants, which may be missed on standard T2W imaging. The 2023 guidelines have divided peritoneal deposits anatomically into pelvic and abdominal peritoneal deposits and downstaged pelvic deposits to stage IIIB2 because of a comparatively better prognosis. Abdominal peritoneal metastases are categorized into a newer subcategory, stage IVB.

Distant Metastases

Distant spread typically occurs via lymphatic or hematogenous routes. The lungs are the most frequent site of hematogenous metastasis, followed by the liver. MRI and CT, in conjunction with PET, when needed, are used to evaluate systemic involvement. All distant metastases are now placed into stage IVC. The presence of distant disease significantly worsens prognosis, with a limited median survival in cases of widespread organ involvement.

Assessing Eligibility for Fertility-Sparing Treatments

Fertility preservation remains an important consideration for young patients with early-stage, low-grade disease. The 2023 FIGO update does not alter the established eligibility criteria. MRI continues to play a central role in determining suitability for conservative management. Pelvic CE-MRI is essential to exclude any myometrial invasion, cervical stromal involvement, skip lesions, or parametrial spread, and synchronous ovarian tumors. It also allows assessment of pelvic lymph nodes and helps identify features that would contraindicate conservative management. Molecular profiling does not influence eligibility, as high-grade endometrioid tumors (where molecular classification is most relevant) are already a contraindication for fertility-sparing treatment. MRI, therefore, remains the most reliable modality for assessing anatomic criteria crucial for fertility-sparing decision-making, monitoring response to hormonal therapy, and detecting early recurrence in those managed conservatively.

Predicting Histopathological Subtypes

Recent studies[10] [11] [12] [13] [14] [15] have highlighted the potential role of MRI in the prediction of histopathological features of EC, in line with the updated FIGO classification. This is particularly important in cases where a biopsy is difficult.

Histological subtype: Emerging evidence suggests that tumor size may provide valuable insight. Non-EECs (NEECs), which are typically more aggressive, have been shown to present with larger tumor dimensions (proposed cutoff: 48 mm) on imaging compared to endometrioid adenocarcinomas (EACs).[11] This distinction, although not definitive in isolation, may assist in risk stratification when combined with other imaging parameters. Pelvic peritoneal implants, when visible on MRI, have also been identified as potential indicators of aggressive tumor biology. They are more frequently associated with NEEC and may serve as noninvasive markers of extrauterine spread. As far as tumor histology is concerned, the role of ADC values remains controversial.[11] [12] [13] [14] Some studies have reported lower ADC values in NEEC supporting the use of ADC as a functional imaging biomarker in differentiating NEEC from EAC[13] [14]; however, variability in measurement techniques continues to limit widespread standardization.

Tumor grade: A significant difference in tumor size has also been observed between low- and high-grade EC, with some studies identifying a cutoff around 32 mm associated with good sensitivity and specificity.[11] High-grade tumors, associated with increased cellularity and nuclear atypia, exhibit significantly lower ADC values compared to low-grade tumors.[11] [16] [17] When an ADC cutoff of around 670 × 10⁻³ mm²/s is applied, sensitivity and specificity values of approximately 70 and 88%, respectively, have been noted.[11] Despite the lack of full consensus in the literature, lower ADC values are generally considered indicative of higher-grade tumors.[11] This is particularly relevant when considering fertility-preserving or ovarian-sparing surgical options. MRI features, such as tumor size and location, especially when confined to the endometrial cavity or arising from a polyp base, can aid in refining staging and supporting individualized management strategies for EC.

LVSI, an established prognostic factor now included in FIGO staging, remains difficult to detect directly on MRI. However, certain imaging features—such as increased tumor size, low ADC values, and the presence of peritoneal implants—have shown associations with LVSI. These surrogate markers may provide indirect but valuable insights into the likelihood of LVSI, contributing to more refined preoperative risk evaluation.

Taken together, these findings suggest that MRI has a growing role in the noninvasive prediction of histopathological features in EC. As the classification of EC continues to evolve with the integration of molecular subtypes—including POLE mutations, MMR, and p53 abnormalities—the potential synergy between MRI and molecular diagnostics presents a promising avenue for future research.

Conclusion

In summary, the 2023 FIGO classification necessitates a nuanced approach to MRI interpretation that incorporates anatomic refinements, molecular profiling, and the clinical context. MRI remains indispensable for staging, treatment planning, and surveillance in EC. Accurate, structured reporting is critical, especially when biopsy data are unavailable or posttreatment anatomy is complex. Integration of molecular insights with MRI may advance future diagnostic precision and individualized care.

Conflict of Interest

None declared.

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Publication History

Article published online:
16 January 2026