Risk of recurrence in patients with MELF (microcystic, elongated and fragmented) pattern of invasion based on lymph node evaluation status

Objectives: Background. Myometrial invasion with an infiltrative gland pattern has been recently associated with higher stage, lymphovascular invasion, and recurrence. Additionally, a readily recognizable pattern of myometrial invasion characterized by microcystic elongated and fragmented (MELF) glands surrounded by myxoid and inflamed stroma has been associated with lymphovascular invasion (LVSI) and lymph node metastases. Although it is known that MELF increases the risk of a patient having lymph node metastases as well as MELF being associated with LVSI, we sought to understand whether MELF without lymph node metastases or lymphadenctomy portends a worse oncologic prognosis. Methods: We retrospectively reviewed all patients with endometrial cancer who underwent hysterectomy at a single institution between Jan 1, 2010 to Aug 1, 2020 with MELF pattern of invasion identified. Pathology was reviewed by a single reviewer (RM) with subspecialty training in gynecologic pathology. The electronic medical record was utilized to obtain preoperative, perioperative, and follow-up data. These patients were divided based on if they had not had a lymph node evaluation (Group A) or by the performance of lymph node evaluation (Group B). Results: Forty-one patients were identified as having MELF on their hysterectomy specimen. All patients had well-differentiated to moderately differentiated tumors. There was a similar proportion of patients how had LVSI in either group (Group A 80% vs Group B 92.3%). In this cohort, 63.4% underwent an evaluation of the retro-peritoneal lymph nodes, with 92.3% having a complete lymphadenectomy [Table 1]. As compared to Group B where only 7.7% had no adjuvant treatment, 53.3% in Group A were observed. No patients recurred in Group B, while 20% recurred in those without any lymph node evaluation. Looking specifically at the patients who had MELF without lymphadenectomy and recurred, all 3 patients had LVSI and were early stage, thus were at high risk for lymph node involvement. Download : Download high-res image (332KB) Download : Download full-size image Conclusions: In our study, patients with MELF pattern of invasion without lymph node evaluation at the time of hysterectomy were more likely to have no adjuvant therapy and recur than those who underwent lymphadenectomy. Additional multi-institution study should be done to further elucidate the nuances associated with MELF with and without LVSI in patients with early stage endometrial cancer who have undergone lymphadenectomy as this uterine characteristic is not factored in to any of our phase III randomized data.