Impact of endometrial sampling technique and biopsy volume on the diagnostic accuracy of endometrial cancer

BACKGROUND: Histotype and tumor grading of endometrial cancer are the most important factors that have to be assessed by preoperative endometrial sampling, and their concordance with the final surgical and definitive histological findings is of paramount importance. We aim to compare histotype and tumor grading concordance of various endometrial sampling techniques (ESTs) and to investigate the role of endometrial volume biopsy. METHODS: We performed a retrospective analysis of patients with apparent early stage endometrial cancer collecting demographic, clinical data, type of EST, pathological characteristics of endometrial biopsies and final specimens. We classified ESTs as dilation and curettage (D&C), diagnostic hysteroscopy with D&C, outpatient hysteroscopy and operative hysteroscopy with or without D&C. Diagnostic and operative hysteroscopy were performed with Bettocchi's 5 mm hysteroscope. We evaluated concordance for histotype, and tumor grading, and we performed subgroup analysis based on the technique and final tumor grading. Concordance was classified from good, moderate, sufficient, fair, poor and none using Cohen k-statistic. Finally, we investigated the existence of independent risk factors for discordant tumor grading using multivariate binary logistic regression. RESULTS: We collected 148 patients and of these 131 (88.5%) were diagnosed with endometrioid histotype and 65 (44%), 46 (31%) and 37 (25%) respectively with well, moderate and poor differentiated tumors. Atypical hyperplasia (AH) was detected preoperatively in 28 patients (19%). Histotype concordance was fair (k=0.35) and tumor grading concordance was moderate (k=0.45); particularly, concordance was fair in well-differentiated cases (k=0.38); concordance was moderate in moderate- and poor-differentiated cases (k=0.52) and good (k=0.71). Operative hysteroscopy showed moderate concordance for histotype (k=0.41), while grading concordance was fair for G1 (k=0.41), moderate for G2 (k=0.58) and good for G3 (k=0.72), regardless the use of D&C. Preoperative volume biopsy did not impact the concordance of tumor grading, while the adoption of operative hysteroscopy (with or without D&C) decreased the risk of grading discordance in G3 tumors (HR 0.17; 95% CI: 0.03-0.94; P=0.04). Conversely, time elapsed from diagnosis to treatment in well-differentiated tumors increased the risk of discordant results (HR 1.06; 95% CI: 1.02-1.52; P=0.04). CONCLUSIONS: Operative hysteroscopy demonstrated the best tumor grading concordance, especially in poor-differentiated tumors. The volume of biopsy did not affect the tumor grading concordance.