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Endometrial Cancer Biomarker testing

Biomarker testing of endometrial cancer is crucial to provide accurate risk stratification and insight into prognosis, inform therapy decisions and predict treatment response.1,2 Additionally, tumours with mismatch repair deficiency (dMMR) and high microsatellite instability (MSI) may indicate an underlying diagnosis of Lynch syndrome, a hereditary cancer syndrome.3

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Molecular classification

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Genetic biomarkers

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Lynch syndrome

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Guidelines on biomarker testing

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Molecular classification 

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The Cancer Genome Atlas (TCGA) endometrial carcinoma study in 2013 resulted in a paradigm shift in the classification of endometrial cancer with the identification of four molecular subtypes. TCGA classification consists of:4,5

  • Polymerase epsilon (POLE) ultramutated
  • MSI hypermutated
  • Copy number low (endometrioid)
  • Copy number high (serous-like)
Features of the four molecular subtypes of endometrial cancer

Table 1. Features of the four molecular subtypes of endometrial cancer.1,6
MSI, microsatellite instability.

The ProMisE algorithm

The ProMisE (Proactive Molecular Risk Classifier for Endometrial Cancer) classification system was based on results from TCGA and assigns patients with endometrial cancer to one of four molecular subgroups POLEmut, mismatch repair-deficient (dMMR), no specific molecular profile (NSMP) or p53 abnormal (p53abn):7-9

Proactive Molecular Risk Classifier for Endometrial cancer (ProMisE) algorithm

Figure 1. Proactive Molecular Risk Classifier for Endometrial cancer (ProMisE) algorithm.9–11
Figure adapted from Talhouk A et al. 20179 and Vermij L et al. 2020.10
dMMR, mismatch repair-deficient; ER, oestrogen receptor; IHC, immunohistochemistry; MMR, mismatch repair; MSS, microsatellite stability; NSMP, no specific molecular profile; p53 abn, p53 abnormal; pMMR, mismatch repair-proficient; POLEmut, POLE mutated; TCGA, The Cancer Genome Atlas; wt, wild type.

The ProMisE classification system is prognostic, showing significant association with disease-specific survival (DSS; p=0.03) and progression-free survival (PFS; p=0.001).8

Progression free survival by molecular subgroups of endometrial tumours

Figure 2. Progression-free survival by molecular subgroups of endometrial tumours4
NSMP, no specific molecular profile; p53abn, p53 abnormal; POLEmut, POLE mutated.

The incidence of the four molecular subgroups has been reported as:

Incidence of molecular subgroups in endometrial cancer

Figure 3. Incidence of molecular subgroups in endometrial cancer.2,12–17
dMMR, mismatch repair-deficient; MSI-H, microsatellite instability-high; MSS, microsatellite stability; NSMP, no specific molecular profile; p53abn, p53 abnormal; pMMR, mismatch repair-proficient; POLEmut, POLE mutated.

The samples of 423 consented patients from the PORTEC3 trial were analysed separately in a translational study which investigated prognosis according to molecular subgroup per the TCGA/ProMisE classification. The samples were classified as POLEmut (12.4%), dMMR (33.4%), p53abn (22.7%) and NSMP (31.5%). The five-year recurrence free and overall survival estimates by molecular subgroup are shown below, with findings confirming the strong prognostic value of the TCGA and ProMisE molecular classification in high-risk endometrial cancer.18

5-year recurrence-free and overall survival by molecular subgroup in the PORTEC-3 trial

Figure 4. 5-year recurrence-free and overall survival by molecular subgroup in the PORTEC-3 trial.18
Figure adapted from León-Castillo et al. 2020.18
mDoF was 6.1 years.
dMMR, mismatch repair-deficient; mDoF, median duration of follow-up; No., number; NSMP, no specific molecular profile; OS, overall survival; p53abn, p53 abnormal; POLEmut, POLE mutated; RFS, recurrence-free survival.

The implementation of molecular classification using TCGA and ProMisE algorithm can help to counsel patients on their prognosis and guide tailored treatment management decisions to improve outcomes for women with endometrial cancer.8

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Genetic biomarkers

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dMMR/MSI-H

The MMR system is responsible for correcting erroneous base insertions, deletions and mis-incorporations that can occur during DNA replication. Microsatellites are short tandem stretches of DNA prone to mismatch errors.2 MSI is a condition of genetic hypermutability resulting from defective DNA MMR and characterised by clustering of mutations in microsatellites, typically evidenced by repeat length alterations. The presence of MSI represents phenotypic evidence that the MMR system is not functioning normally.19

The four genes that play a critical role in the MMR process include MLH1, MSH2, MSH6 and PMS2. Inactivation of one of these genes, which can occur as a result of germline and/or somatic mutations or epigenetic silencing, results in dMMR.19

Approximately 30% of endometrial cancers have MSI, which may arise from somatic or germline alterations increasing the risk of developing endometrial cancer.2,20

Watch this video from Siobhan John, Cancer Nurse Specialist, describing the difference between somatic and germline mutations.

Testing for dMMR/MSI

The European Society for Medical Oncology (ESMO) guidelines recommend using MMR immunohistochemistry (IHC) as standard practice for determining MSI in all endometrial cancer pathology specimens regardless of histological subtype.19 IHC, polymerase chain reaction (PCR) and next-generation sequencing (NGS) are frequently used techniques for measuring protein and genomic biomarkers.21 MMR testing is carried out in over 90% of endometrial cancer tumours, predominantly by IHC, see Figure 5.22 A summary of the advantages and limitations of IHC, PCR and NGS are detailed in Table 2.

MMR/MSI testing workflow according to ESMO recommendations

Figure 5. MMR/MSI testing workflow according to ESMO recommendations.19,23
*NGS represents an alternative molecular test to assess MSI.19
ESMO, European Society for Medical Oncology; IHC, immunohistochemistry; dMMR, mismatch repair-deficient; MMR, mismatch repair; MMRp, mismatch repair-proficient; MSI-H, microsatellite instability-high; MSI-L, microsatellite instability-low; MSS, microsatellite stability; NGS, next-generation sequencing; PCR, polymerase chain reaction.

  IHC24,25 PCR21,25,26 NGS21,27
Analyses Protein presence; morphologic tissue changes Genetic sequences Whole genome; targeted genes
Advantages Low cost; short turnaround time Moderate cost; short turnaround time Provides details on all genomic mutations
Limitations Tissue fixation may cause variability Unable to perform highly multiplex assays Requires specialist equipment; long turnaround time
Summary Accessible and low-cost way to detect expressed proteins Widely used for DNA sequencing; provides accurate quantification and high sensitivity Provides a large amount of genetic information, but only select data have clinical relevance

Table 2. IHC, PCR and NGS testing overview
IHC, immunohistochemistry; NGS, next-generation sequencing; PCR, polymerase chain reaction.

Genetic biomarkers

  • POLE is a DNA replicate responsible for the low mutation rate in eukaryotic DNA replication. Mutations in the proofreading domain of POLE result in a high mutational frequency.6

    Mutations in POLE are associated with hypermutated tumours with a favourable prognosis; somatic mutations in POLE have been identified in 7–9% of endometrial tumours.2,12,16

    POLE status is tested using NGS on endometrial biopsy samples via NHS Genomic Laboratory Hubs. This is available for NHS patients through national genomics service in the UK.28

  • Somatic mutations of the tumour suppressor gene TP53 are found in approximately 15–20% of all endometrial cancers. TP53 mutation is a validated biomarker associated with poor prognosis in endometrial cancer.2,6,15

    p53 IHC staining has been shown to be an excellent surrogate marker for TP53 mutational status as determined by sequencing in endometrial cancer biopsies.29

    IHC is recommended for p53 status testing, although mutational analysis via NGS is the alternative used when IHC is equivocal or heterogeneous.11

Additional biomarkers

While TCGA biomarkers serve a prognostic role, clinical research is ongoing to assess the prognostic and predictive function of other biomarkers. Biomarker testing beyond TCGA molecular subtypes includes:2

  • Hormone receptor status (oestrogen receptor [ER] and progesterone receptor [PR])
  • Human epidermal growth factor receptor 2 (HER2)
  • Programme death ligand-1 (PD-L1)
  • Tumour mutational burden (TMB)

  • ER/PR

    ER and PR positivity has not been shown in a systematic review, but a case example in a Chinese cohort of 89 patients diagnosed with endometrial cancer, showed expression was present in approximately update to 60% and 75%, respectively.30 The British Association of Gynaecological Pathologists and the British Gynaecological Cancer Society (BAGP/BGCS), as well as the European Society of Gynaecological Oncology, European Society for Radiotherapy and Oncology and European Society of Pathology(ESGO/ESTRO/ESP) 2025 endometrial cancer management guidelines recommend ER status should be tested by IHC in all cases of endometrial carcinomas as it can facilitate diagnosis, is prognostic in the NSMP group, and is predictive for response to endocrine therapy in advanced and recurrent disease.11,28

  • HER2

    HER2 is an established biomarker that is overexpressed in approximately 30% of endometrial serous carcinomas, a subtype of endometrial cancer associated with poor outcomes and high mortality.2

    Most cases of HER2 overexpression are caused by gene amplification and can be detected either by IHC, fluorescent in situ hybridisation (FISH) or NGS.2

    The ESGO/ESTRO/ESP endometrial cancer management guidelines 2025 recommend all advanced and recurrent p53abn endometrial carcinomas and all serous carcinomas or carcinosarcomas may be tested for HER2 overexpression by IHC and, in case of an immunoreactive score of 2 or more, by in situ hybridisation using standardised criteria.11 HER2 overexpression may indicate suitability for HER2-targeted treatment for patients with advanced stage or recurrent endometrial tumours.2

  • PD-L1

    The PD-1 pathway plays a vital role in maintaining peripheral tolerance by suppressing T-cell activity. Tumours often express PD-L1 to suppress immune surveillance and facilitate tumour growth.31

    PD-L1 expression is observed in approximately one-third of endometrial cancers.32

    PD-L1 expression is assessed by IHC and is expressed to varying degrees in different tumour types.33 Whilst PD-L1 is used to inform targeted therapy in other tumour types, there is so far no clear evidence in endometrial cancer that it can be used as a predictive biomarker.34

  • TMB

    TMB is a biomarker defined as the total number of somatic mutations per coding area of a tumour genome, obtained through NGS.2

    Tumours with >10 mutations/Mb, such as POLEmut and dMMR endometrial cancers, are referred to as TMB-high (TMB-H). TMB-H is found in approximately 43% of endometrial cancers.35 TMB-H is associated with high-grade tumours and correlates with improved overall survival compared with non-TMB-H tumours.35,36

Timely availability of biomarker test results

In the UK, according to a survey conducted by the BAGP and the BGCS, 85% of clinicians have access to molecular classification testing.37

This is usually carried out with a combination of MMR and p53 IHC and POLE sequencing. While the first two are universally available across the UK, POLE testing has only been available nationally since April 2023; the UK figure is therefore largely a surrogate for the availability of POLE testing.37

Overall, only 36% of the clinicians surveyed reported always or usually receiving timely test results, defined as in time to affect decision-making and stage allocation at the gynaecological oncology multidisciplinary team meeting.37

Classification and biomarker testing can inform treatment decisions. Click here to learn more about the treatment landscape of endometrial cancer
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Lynch syndrome

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Lynch syndrome

Lynch syndrome, which may also be referred to as hereditary non-polyposis colorectal cancer (HNPCC), is an autosomal dominant genetic condition caused by germline mutations in the MMR genes or deletion of EPCAM (which inactivates MSH2).3

Endometrial cancer is often the first cancer diagnosis in women with Lynch syndrome.38 The lifetime risk of developing endometrial cancer in patients with Lynch syndrome is 15–60%, depending on the specific gene mutation.39

The National Institute for Health and Care Excellence (NICE), BGCS and ESGO all recommend testing for MMR status as part of screening for Lynch syndrome, which is funded by the NHS for all patients diagnosed with endometrial cancer.11,40–42

Step 1

  • A four-panel IHC test for MLH1, MSH2, MSH6 and PMS2
    • If MSH2, MSH6 or PMS2 IHC results are abnormal, confirm Lynch syndrome by genetic testing of germline DNA

Step 2

  • If the IHC results for MLH1 (or MLH1 and PMS2) are abnormal, use MLH1 promoter hypermethylation testing on tumour DNA to differentiate sporadic and Lynch syndrome-associated endometrial cancer

Step 3

  • If the MLH1 promoter hypermethylation is negative, confirm Lynch syndrome by genetic testing of germline DNA

A retrospective study looking at the implementation of Lynch syndrome testing in endometrial cancer in the UK and Ireland found that less than 1% of the tested cohort were diagnosed with Lynch syndrome, suggesting numerous cases were missed. Despite high rates of MMR testing (91%), substantial diagnostic attrition occurs during hypermethylation analysis, counselling referrals and germline testing. These results highlight the need to integrate mainstreamed genetic testing into routine clinical care to reduce delays and improve patient access to testing.22

Patients with endometrial carcinoma identified as having an increased risk of Lynch syndrome by MMR IHC (with or without MLH1 methylation analysis) or MSI testing or family history should be offered genetic counselling.11

The English National Lynch Syndrome Transformation Project

The English National Lynch Syndrome Transformation Project, led through the Genomic Medicine Service Alliances (GMSAs), has embedded genomics into cancer multidisciplinary teams (MDTs) across England, establishing mainstreaming teams, expanding access to diagnostic testing, and implementing NICE guidance (HealthTech guidance 430 and 557), as detailed in a recent International Journal of Cancer publication in January 2026.43 The project was initially funded by NHS England for 1 year (2021/2022), but funding was then extended into 2022/2023 and 2023/2024 due to early progress and impact seen. Transitional support was then allocated for 2024/2025 to support the move towards integration into NHS ‘business as usual’.

key results from implementation of this project included:

  • Establishment of support networks (local, regional and national) for local Lynch Syndrome champions. At study completion, 94% of 119 gynae-oncology MDTs nationally reported having a local LS champion
  • An increase in national MMR testing rates from 19% to 95% for endometrial cancer, with every region achieving MMR testing rates above 91% (range: 92–100%)
  • In a survey conducted at project completion, which included 45 colorectal cancer and 32 gynae-oncology Lynch syndrome champions:
    • Tumour MMR testing results were more likely to be discussed and documented at MDT meetings, with clearer responsibility for the specific MDT clinician identified who would arrange the next step in the testing pathway for both colorectal cancer and endometrial cancer (83.3% in 2025 vs. 64.2% in 2021; p<0.001)
    • 44 respondents (57%) indicated that their teams were delivering in-house mainstreamed genetic testing, while 15 teams (19%) reported they were in the process of transitioning to a mainstreamed model across colorectal cancer and endometrial cancer 
    • By 2024, mainstreamed pathways were in place in 41% of gynaecological oncology teams across England, representing a major shift toward localised delivery of genomic medicine within multidisciplinary cancer services
  • An increase of 4% new diagnoses annually over the project lifetime from 2020 to 2024

Lynch syndrome mainstreaming video series

Explore the videos below to learn more about Lynch syndrome and the implementation of mainstreaming.

The Lynch Syndrome mainstreaming video series is a non-promotional, educational resource to support Lynch Syndrome Cancer Nurse Specialists (CNS) with implementation of mainstreaming in practice but also for the wider multi-disciplinary team to better understand Lynch Syndrome testing and the role of the Lynch Syndrome CNS. 

These videos have been designed to be viewed either in sequence or by choosing the specific video dependent on the topic of interest. These videos do not replace the advice of the genetic counsellor. Please seek the advice of your regional Lynch Syndrome CNS or your GMSA for support and information.

The Lynch Syndrome mainstreaming educational videos were co-created and funded by GSK. The speakers have been given an honorarium by GSK for their participation in the videos.

Lynch Syndrome Video 1 - Welcome to the National Lynch Mainstreaming Videos

Lynch Syndrome Video 2 - A Brief Description of Lynch Syndrome

Lynch Syndrome Video 3 - The Importance of Mainstreaming

Lynch Syndrome Video 4 - Setting Up a Mainstreaming Clinic

Lynch Syndrome Video 5 - National Genomic Test Directory Criteria: R210

Lynch Syndrome Video 6 - Somatic Versus Germline Mutations

Lynch Syndrome Video 7 - Making a Pedigree

Lynch Syndrome Video 8 - Understanding Mismatch Repair and Microsatellite Instability

Lynch Syndrome Video 9 - Knudson Two- Hit Hypothesis

Lynch syndrome Video 10 - Understanding Results

Lynch Syndrome Video 11 - Consultation in Action (Roleplay)

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Guidelines on biomarker testing

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Guidelines on biomarker testing

Various national and international guidelines have published recommendations on biomarker testing in endometrial cancer.

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In August 2025, ESGO, ESTRO, and ESP published joint guidelines on the management of endometrial cancer, including assessment of molecular classification.11

Algorithm for the assessment of molecular classification of endometrial cancer

Figure 6. Algorithm for the assessment of molecular classification of endometrial cancer.11
Adapted from Concin N et al 2025.11
dMMR, mismatch repair-deficient; ER, oestrogen receptor; G, grade; MMR, mismatch repair; NSMP, no specific molecular profile; p53abn, p53 abnormal; POLEmut, POLE mutated.

Recommendations include:11

  • Molecular classification should be done for all types of endometrial carcinoma and requires three basic analyses including POLEmut, dMMR and p53/TP53 (Figure 6)
  • Molecular testing on endometrial biopsy and curettage material is encouraged; this needs to be repeated on hysterectomy specimens only in specific situations, such as: 
    • Scant tumour tissue on biopsy
    • Equivocal results or technical problems on biopsy
    • In the presence of an additional tumour component in the hysterectomy specimen that was not present in the biopsy
  • Endometrial carcinoma with multiple classifier features should be classified according to their genomic driver, such as a pathogenic POLE mutation (combination of POLEmut with p53abn or dMMR, or both) or MMR deficiency (combination of dMMR with p53abn)
  • The development of clinical trials driven by molecular classification and biomarkers is recommended to further strive towards precision medicine in the management of patients with endometrial carcinoma

BAGP, in collaboration with the BGCS, has published guidance on biomarker testing for endometrial cancer with the recommendation to carry out IHC for MMR, p53 and ER on all endometrial tumour biopsies.28

POLE NGS testing via national genomic services requires considerable resources and presents a barrier to adoption. The algorithm shown in Figure 7 was proposed in  BAGP/BGCS guidelines to manage restricted resource at the time of being written.28

Guidelines on biomarker testing

BAGP and BGCS recommendation for POLE NGS testing in endometrial cancer

Figure 7 BAGP guidance on POLE NGS testing in endometrial carcinoma

Figure adapted from The BAGP and the BGCS. POLE NGS testing guidance 2022.28

BAGP, The British Association of Gynaecological Pathologists; BGCS, British Gynaecological Cancer Society; ER, oestrogen receptor; IHC, immunohistochemistry; LVSI, lymphovascular space invasion; MDT, multidisciplinary team; MMR, mismatch repair; NGS, next generation sequencing

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