Cytological criteria of endometrial lesions with emphasis on stromal and epithelial cell clusters: result of 8 years of experience with intrauterine sampling

Objective:  There are a number of unresolved issues in endometrial cytology. They include the significance of nuclear atypia for the diagnosis of grade1 adenocarcinoma (G1AC) and atypical endometrial hyperplasia (AEH), cytological criteria of endometrial hyperplasia without atypia, and recognition of stromal cell cluster (SC) and its distinction from epithelial cell cluster (EC). Methods:  We examined nuclear atypia, SC and EC in typical cases of five categories: normal endometrium (NEM), simple endometrial hyperplasia without atypia (SEH), complex endometrial hyperplasia without atypia (CEH), G1AC and grade2 adenocarcinoma (G2AC). We classified EC into four types: simple EC (SPEC), large regular EC (LREC), large irregular EC (LIEC) and small irregular EC (SIEC). Based on the results, we developed criteria of endometrial cytology and have evaluated 13 639 cases over 8 years. Results:  Nuclear atypia was significantly more frequent in G2AC than in any of the other four categories (P < 0.001). SC was significantly more frequent in NEM and SEH than in the other three categories (P < 0.001). G1AC and G2AC showed significantly higher frequency of LIEC than the other three categories (P < 0.001). CEH exhibited significantly higher frequency of LREC than the four categories (P < 0.001). The sensitivity and the specificity was 88.8% and 99.0% respectively. Conclusions:  We could diagnose G1AC, G2AC and CEH with high accuracy using the established criteria mainly based on SC and EC. We think that the criteria may facilitate an effective screening and an objective interpretation of endometrial samples.