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#537 Germinal mutation study of lynch syndrome in patients affected by endometrial cancer with microsatellite inestability
  1. Blanca Fernandez,
  2. Marina Matute,
  3. Julene Saornil,
  4. Itziar Gonzalez,
  5. Juan Cespedes,
  6. Ibón Jaunarena,
  7. Ruben Ruiz,
  8. Paloma Cobas,
  9. Arantxa Lekuona and
  10. Mikel Gorostidi
  1. Hospital Universitario Donostia, Donostia, Spain


Introduction/Background Endometrial cancer (EC) that express a deficit in DNA missmatch repair proteins (MMRd), it is necessary to rule out a germinal mutation related to Lynch Syndrome (LS). MMRd is described in 20–40% of EC, 10% related to LS. Of all EC, 3% are related to Sd Lynch. Detection of EC with MMRd at an early stage, to date, does not imply a change in complementary treatment, a fact that changes in advanced disease who benefit from immunotherapy as 2nd line. The aim of this study is to analyze patients diagnosed with MMRd EC and its association with LS.

Methodology Retrospective descriptive cohort study.

Molecular profile data of EC has been collected from patients that underwent surgery since the implementation of this classification in our hospital, from February-2021 to January-2023.

Results A total of 117 patients with EC, 24 resulted MMRd, which corresponds to 20.5%. The median age is 60 years (38–81 years). The most frequent histology is endometrioid adenocarcinoma (23/24), only one undifferentiated carcinoma. 12 of the patients were in stage IA, 6 patients IB, 1 patient II, 2 in IIIA, 1 in IIIC1 and 2 in IIIC2. Only one adenocarcinoma with MMRd-POLE mutated multiclassification, a patient with stage IA G3 who was omitted from complementary treatment due to good prognosis according to POLEmut.

Of all the patients with MMRd EC, 2 were found to be related to LS, this relationship was ruled out in 2, and 3 patients remain awaiting results. MLH1 hypermethylation was found in 17 patients. One patient, the youngest, had already been previously diagnosed with LS as a result of a family history study.

Conclusion Currently, the MMRd molecular profile does not imply a change in adjuvant treatment in early stages.

EC with MMRd is more probably to be sporadic due to MLH1 hipermethylation than linked to LS.

Disclosures Close relationship of MMRd with endometrioid adenocarcinoma of the endometrium.

Most MMRd are secondary to MLH1 hypermethylation and not related with Lynch Syndrome.

Not many cases of molecular multiclassification are found.

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