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. 2025 Sep;487(3):511-522.
doi: 10.1007/s00428-025-04132-3. Epub 2025 Jun 5.

EPM2 AIP1 immunohistochemistry as a surrogate of promoter methylation analysis in endometrial carcinoma

Sonia Gatius  1 , Marta Vaquero  2 , Oliver Scheiber  3 , Ana Velasco  2 , Dolors Cuevas  2 , Karl Kashofer  4 , Maria Santacana  5 , Núria Eritja  6 , Sigurd Lax  3   7 , Xavier Matias-Guiu  8
Affiliations

EPM2 AIP1 immunohistochemistry as a surrogate of promoter methylation analysis in endometrial carcinoma

Sonia Gatius et al. Virchows Arch. 2025 Sep.

Abstract

Mismatch repair (MMR) status in endometrial carcinoma (EC) is crucial for diagnosis, prognosis, treatment, and Lynch syndrome pre-screening. MLH1 loss is the most frequent cause of MMR deficiency and usually by promoter hypermethylation. We tried to confirm the role of EPM2 AIP1 immunohistochemistry as a surrogate of MLH1 promoter methylation in EC. Case series from two different institutions were analyzed by comparable methods using immunohistochemistry for MMR proteins and EPM2 AIP1, and pyrosequencing for MLH1 methylation. In the first series of 70 cases, concordance was 100%, after reassessing three cases with methylation scores close to cut-off, by tumor cell enrichment. In the second series of 29 MLH1-deficient ECs, concordance was 96.5%, while in the control group of 30 MMR-proficient EC, one MLH1-positive case was EPM2 AIP1-negative. EPM2 AIP1 immunoreactivity was qualitatively superior in curettages and biopsies compared to hysterectomy. We conclude that EPM2 AIP1 immunohistochemistry is a good surrogate for MLH1 promoter methylation analysis, cost-effective with short turnaround time, but needs attention regarding preanalytical handling, normal tissue contamination, or low tumor percentage.

Keywords: EPM2AIP1; Endometrial cancer; Lynch syndrome; MLH-1 methylation.

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Conflict of interest statement

Declarations. Ethics approval and consent to participate: All samples were collected following the current regulations in the biomedical research law, the Royal Decree of Biobanks RD 1716/2011, the European Regulation 2016/679, and the organic law LOPD-GDD 3/2018 on the protection of personal data, and all patients signed an informed consent. The study was approved by local Ethics Committees, in accordance with the Declaration of Helsinki. Conflict of interest: The authors declare no competing interests.

Figures

Fig. 1
Fig. 1
Representative images of EPM2 AIP1 immunohistochemistry and promoter methylation chart of one example of EC with MLH1 hypermethylation A, and one example of EC without MLH1 hypermethylation B. Representative images of MLH1 and EPM2 AIP1 immunohistochemistry in one EC with normal expression of both proteins (control case) C
Fig. 2
Fig. 2
Representative images of an EC with MLH1 deficiency, absence of MLH1 promoter methylation, and positive EPM2 AIP1 immunostaining. The tumor exhibited biallelic somatic alteration of MLH1; one pathogenic variant in MLH1 (NM_000249.4): p.Glu633 Ter (c.1897G > T), classified as a stop-gained mutation, truncating the MLH1 protein, as well as loss of heterozygosity (LOH) detected in chromosomal region 3p22.2-q27.1
Fig. 3
Fig. 3
Representative images of an EC with MLH1 with a methylation score close to the cut-off. The initial biopsy A showed negative EPM2 AIP1 immunostaining and a methylation score of 9.8. In the surgical specimen B, EPM2 AIP1 immunostaining was negative, but the methylation score increased to 60% after tumor microdissection
See this image and copyright information in PMC

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