The pattern of Myometrial invasion as a predictor of lymph node metastasis or Extrauterine disease in low-grade endometrial carcinoma

The purpose of this study was to examine predictors of lymph node (LN) metastases or extrauterine disease (ED) in low-grade (FIGO grade 1 or 2) endometrioid carcinoma (LGEC) in a multi-institutional setting. For LGEC with and without LN metastasis or ED, each of the 9 participating institutions evaluated patients' age, tumor size, myometrial invasion (MI), FIGO grade, % solid component, the presence or absence of papillary architecture, microcystic, elongated, and fragmented glands (MELF), single-cell/cell-cluster invasion (SCI), lymphovascular invasion (LVI), lower uterine segment (LUS) and cervical stromal (CX) involvement, and numbers of pelvic and para-Aortic LNs sampled. A total of 304 cases were reviewed: LN or ED, 96; LN/ED, 208. Patients' ages ranged from 23 to 91 years (median 61 y). Table 1 summarizes the histopathologic variables that were noted for the LN or ED group: tumor size ≥2 cm, 93/96 (97%); MI>50%, 54/96 (56%); MELF, 67/96 (70%); SCI, 33/96 (34%); LVI, 79/96 (82%); >20% solid, 65/96 (68%); papillary architecture present, 68/96 (72%); LUS involved, 64/96 (67%); and CX involved, 41/96 (43%). For the LN/ED group, the results were as follows: tumor size ≥2 cm, 152/208 (73%); MI>50%, 56/208 (27%); MELF, 79/208 (38%); SCI, 19/208 (9%); LVI, 56/208 (27%); >20% solid, 160/208 (77%); papillary architecture present, 122/208 (59%); LUS involved, 77/208 (37%); CX involved, 24/208 (12%). There was no evidence of a difference in the number of pelvic or para-Aortic LNs sampled between groups (P=0.9 and 0.1, respectively). After multivariate analysis, the depth of MI, CX involvement, LVI, and SCI emerged as significant predictors of advanced-stage disease. Although univariate analysis pointed to LUS involvement, MELF pattern of invasion, and papillary architecture as possible predictors of advanced-stage disease, these were not shown to be significant by multivariate analysis. This study validates MI, CX involvement, and LVI as significant predictors of LN or ED. The association of SCI pattern with advanced-stage LGEC is a novel finding.