Architectural versus nuclear atypia-defined FIGO grade 2 endometrial endometrioid adenocarcinoma (EEC): a clinicopathologic comparison of 154 cases with clinical follow-up.

International Federation of Gynecology and Obstetrics (FIGO) Grade 2 endometrial endometrioid adenocarcinoma carries a 88% 5-yr survival rate. They are defined by >5% but <50% solid epithelial component. A small subset may display <5% solid growth, but marked nuclear atypia and are designated Grade 2. We compared tumor characteristics, staging, and clinical outcome of patients with architectural versus atypia-defined Grade 2 endometrial endometrioid adenocarcinoma. A total of 154 Grade 2 endometrial endometrioid adenocarcinoma cases were reviewed to confirm grade; percent solid growth, and presence of atypia. Only marked atypia (significant nuclear pleomorphism identifiable at 10× or enlarged nuclei, 1.5 to 2× normal, with irregular nuclear contours, dispersed chromatin, and prominent nucleoli) increased the FIGO Grade 1 level. Depth of invasion, tumor stage, lymph node status, and clinical outcomes were then compared. A total of 154 cases were evaluated. Twenty-three were eliminated (6 Grade 3, 17 Grade 1). Of the 131 FIGO II cases, 19 (15%) were based on the presence of severe atypia and 112 (85%) met the architecturally defined criteria. Atypia-defined versus architecturally defined Grade 2 endometrial endometrioid adenocarcinoma's show no significant difference in stage and prognosis. An increase in grade based on presence of nuclear atypia stratifies patients at increased risk as 89% of these patients have myoinvasion at the time of hysterectomy which is in distinct contrast to our previous study (International Journal of Gynecologic Pathology. 2012 July; 31(4): 337-43), where 70% of Grade I cases were noninvasive. No significant correlation between percentage of solid component and risk of recurrence was identified in this study.