Background: Microcystic, elongated, and fragmented (MELF) invasion is a special invasion pattern in endometrioid endometrial cancer (EEC). This study aimed to investigate the clinical, pathological, and molecular features of the MELF pattern and its prognostic value in patients with EEC.Materials and Methods: The clinical and pathological data of 342 patients with EEC were retrospectively collected at Peking University People’s Hospital from January 2019 to December 2022. Some key clinicopathological features were evaluated, including the tumor grade, Federation of Gynecology and Obstetrics (FIGO) staging, cervical stromal involvement, lymph node status, and lymphatic vascular space infiltration (LVSI). Immunohistochemical staining and molecular tests were performed, and the relevant literature was reviewed.Results: The MELF pattern was more prevalent in low-grade EEC. A significant correlation was found between the MELF pattern and advanced FIGO staging, LVSI, the depth of myometrial invasion, cervical stromal involvement, and lymph node metastasis (LNM). The incidence of mismatch-repair-deficient (MMRd) proteins was much higher in the MELF group than in the no-MELF group. Molecular testing revealed that, after copy number—low (CNL), microsatellite instability—high (MSI-H) was the second-most frequent subtype in the MELF group. The recurrence risk did not significantly differ between the MELF and no-MELF groups, but the differences among the four molecular subtypes were statistically significant. However, the MELF group experienced a shorter recurrence time. Among the four molecular subtypes, the recurrence risk was the highest in the CNH subgroup, followed by the MSI-H subgroup.Conclusions: MELF is a special invasion pattern in EEC and is associated with distinct clinicopathological and molecular characteristics, including the latest 2023 FIGO staging. Further research is warranted to explore its implications for treatment strategies and patient outcomes.
背景：微囊、拉长及碎片状（MELF）浸润是子宫内膜样腺癌（EEC）中一种特殊的浸润模式。本研究旨在探讨MELF模式的临床、病理及分子特征，及其在EEC患者中的预后价值。 材料与方法：回顾性收集2019年1月至2022年12月北京大学人民医院342例EEC患者的临床及病理资料。评估了包括肿瘤分级、国际妇产科联盟（FIGO）分期、宫颈间质受累、淋巴结状态及淋巴血管间隙浸润（LVSI）在内的关键临床病理特征。进行了免疫组化染色及分子检测，并对相关文献进行了综述。 结果：MELF模式在低级别EEC中更为常见。研究发现MELF模式与晚期FIGO分期、LVSI、肌层浸润深度、宫颈间质受累及淋巴结转移（LNM）显著相关。错配修复缺陷（MMRd）蛋白的发生率在MELF组显著高于非MELF组。分子检测显示，在MELF组中，拷贝数低（CNL）之后，微卫星不稳定性高（MSI-H）是第二常见的亚型。MELF组与非MELF组的复发风险无显著差异，但四种分子亚型间的差异具有统计学意义。然而，MELF组的复发时间更短。在四种分子亚型中，CNH亚组的复发风险最高，其次是MSI-H亚组。 结论：MELF是EEC中一种特殊的浸润模式，与包括最新2023年FIGO分期在内的独特临床病理及分子特征相关。需要进一步研究以探讨其对治疗策略和患者预后的影响。
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