Reproducibility and prognostic value of histologic type and grade in early epithelial ovarian cancer

From September 1981 to September 1986, 417 consecutive treated patients with epithelial ovarian cancer FIGO stage I and II were registered by the Danish Ovarian Cancer Group (DACOVA). Typing and grading were primarily performed by several pathologists, with and without training in gynecologic pathology. Review typing by one specially trained pathologist showed an agreement rate of 72% for serous and endometrioid carcinoma, 86% for mucinous and 100% for clear cell carcinoma. The agreement rate was calculated for patients primarily classified by pathologists trained in gynecologic pathology and for patients primarily classified by pathologists with and without training. The agreement rate was not better for the group of pathologists with special training in gynecologic pathology. Grading was performed according to two classifications: one based on architectural pattern and one on combined criteria. Review grading showed an agreement rate of 77% for architectural classification and an agreement rate of 52% for combined classification. The agreement rate between the two grade classifications at review was only 62%. Combined grading showed a significant tendency towards classifying more tumors as low grade. All grade classifications had prognostic value. The poor agreement rate of both type and grade even when performed by pathologists with expertise in gynecologic pathology, calls for a better and more reproducible characterization of malignant ovarian tumors.