Introduction/Background*Determining the degree of myometrial infiltration allows establishing the best therapeutic approach for each patient as it is an important factor in predicting nodal metastases.

Few prospective studies comparing the diagnostic performance of transvaginal ultrasound (TVS) and magnetic resonance imaging (MRI) in the preoperative local staging of endometrial carcinoma have been reported. In fact, a recent meta-analysis has shown that both techniques have similar diagnostic accuracy. However, to the best of our knowledge, there has been no prospective comparison of the diagnostic performance of TVS and MRI in the same group of patients with low-grade endometrial cancer.

The aim of this study was to analyse which factors could influence the ultrasound assessment of the myometrial infiltration.

Methodology Observational prospective study performed at a single tertiary care centre from 2016 to 2020, comprising 156 consecutive patients diagnosed by endometrial sampling as having an endometrioid grade 1/grade2 endometrial cancer. TVS and MRI were performed prior to surgical staging for assessing MI, which was estimated using subjective examiner’s impression and Karlsson’s method for both TVS and MRI. During surgery, intraoperative assessment of MI was also performed. Definitive pathological study considered as reference standard.

Univariate logistic regression model has been used to study the association between potential confounding variables adn the ultrasound assessment of myometrial infiltration.

Result(s)*Variables such as age older than 65 years old, endometrial thickness determined by ultrasound greater than 15 mm, ultrasound pattern of moderate-abundant vascularization, definitive G3 histological grade and presence of lymphovascular invasion in definitive AP study are related to a higher risk of ultrasound misclassification. The first three variables tend to cause an overestimation fo the MI degree, while the last two tend to cause its underestimation.

Conclusion*When assessing myometrial infiltration by transvaginal utlrasound we should remind that there are some counfunding variables which could make us misclasiffy myometrial infiltration.