Background: The histologic grade of endometrial adenocarcinoma is related to the aggressiveness of the tumor and probability of death from disease. However, the ideal system for assignment of histologic grade remains controversial. In 1988, the International Federation of Gynecology and Obstetrics (FIGO) revised its recommendations for grading typical endometrial adenocarcinoma, such that grade is determined primarily by the architecture of the tumor and secondarily modified in the presence of "notable nuclear atypia"; this phrase, however, has never been defined, and therefore the prognostic validity of this system is unknown.
Methods: Seven hundred and fifteen women with clinical Stage I and occult Stage II endometrial adenocarcinomas (excluding serous or clear cell type) entered on a Gynecologic Oncology Group protocol, and those treated by total abdominal hysterectomy, bilateral salpingo-oophorectomy, and selective pelvic and para-aortic lymph node sampling formed the study population. All cases were centrally reviewed and assigned an architectural grade and a nuclear grade using specific criteria. The FIGO grade was then determined. The various grading methods were examined based on ability to stratify patients into groups with differing rates of disease progression and relative survival at five years.
Results: The architectural grade, nuclear grade, and FIGO grade of tumors each were used to separate patients into groups with statistically significant different rates of progression of disease and relative survival. The FIGO modification of architectural grade resulted in the reassignment of 44 patients into a higher grade. The outcome for these 44 was worse than for the remaining patients in the initial grade but was similar to the group into which they were moved.
Conclusions: If clearly specified criteria for architectural and nuclear grading are used and "notable nuclear atypia" is defined as grade 3 nuclei, the 1988 FIGO grading system has prognostic utility. The authors recommend this system as the standard method for the grading of typical endometrial adenocarcinoma.