OBJECTIVES: To describe sonographic features of the microcystic elongated and fragmented (MELF) pattern of myometrial invasion (MI) using the International Endometrial Tumor Analysis (IETA) criteria; to assess the effect of the MELF pattern on preoperative ultrasound evaluation of MI; and to determine the relationship of the MELF pattern to more advanced stage (≥ IB) and lymph node metastases in women with endometrioid endometrial cancer. METHODS/MATERIALS: We included 850 women with endometrioid endometrial cancer from the prospective IETA 4 study. Ultrasound experts performed all ultrasound examinations, according to the IETA protocol. Reference pathologists assessed the presence or absence of the MELF pattern. Sonographic features and accuracy of ultrasound assessment of MI were compared in cases with the presence and the absence of the MELF pattern. The MELF pattern was correlated to more advanced stage (≥IB) and lymph node metastases. RESULTS: The MELF pattern was present in 197 (23.2%) women. On preoperative ultrasound imaging the endometrium was thicker (p = 0.031), more richly vascularized (p = 0.003) with the multiple multifocal vessel pattern (p < 0.001) and the assessment of adenomyosis was more often uncertain (p < 0.001). The presence or the absence of the MELF pattern did not affect the accuracy of the assessment of MI. The MELF pattern was associated with deep myometrial invasion (≥ 50%) (p < 0.001), cervical stromal invasion (p = 0.037), more advanced stage (≥ IB) (p < 0.001) and lymph node metastases (p = 0.011). CONCLUSIONS: Tumors with the MELF pattern were slightly larger, more richly vascularized with multiple multifocal vessels and assessment of adenomyosis was more uncertain on ultrasound imaging. The MELF pattern did not increase the risk of underestimating MI in preoperative ultrasound staging. Tumors with the MELF pattern were more than twice as likely to have more advanced stage (≥ IB) and lymph node metastases.

3rd Faculty of Medicine Charles University Prague Czech Republic

Center of Obstetrics and Gynecology Vilnius University Hospital Santariskiu Clinic Vilnius Lithuania

Clinic of Obstetrics and Gynecology University of Milan Bicocca San Gerardo Hospital Monza Italy

Department of Clinical Science and Education Södersjukhuset Stockholm Sweden

Department of Obstetrics and Gynecology Catholic University of the Sacred Heart Rome Italy

Department of Obstetrics and Gynecology Karolinska University Hospital Stockholm Sweden

Department of Obstetrics Gynecology and Reproduction Hospital Universitario Dexeus Barcelona Spain

Department of Pathology 1st Faculty of Medicine Charles University Prague Czech Republic

Department of Pathology and Cytology and Institution for Oncology Pathology Karolinska University Hospital and Karolinska Institutet Stockholm Sweden

Department of Pathology and Cytology Hospital Universitario Dexeus Barcelona Spain

Department of Pathology Catholic University of the Sacred Heart Rome Italy

Department of Women's and Children's Health Karolinska Institutet Stockholm Sweden

Division of Pathology European Institute of Oncology Milan Italy

Gynecological Oncology Center Department of Obstetrics and Gynecology 1st Faculty of Medicine Charles University Prague Czech Republic

Institute for the Care of Mother and Child Prague Czech Republic

Institute for the Care of Mother and Child Praque Czech Republic

National Centre of Pathology Vilnius Lithuania

Pathology Unit San Gerardo Hospital Monza Italy

Preventive Gynecology Unit European Institute of Oncology Milan Italy

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