High-Frequency Ultrasound Imaging for Intraoperative Ex-Vivo Lymph Node Assessment in Gynecological Cancers: Extemporary Analysis Supporting Clinical and Surgical Decision-Making – Preliminary Results of the RHINOCERUS Prospective Trial

Background: Accurate assessment of lymph node status represents a crucial step in the management of gynecologic malignancies, directly influencing staging, prognosis, and treatment strategies. In this context, real-time intraoperative evaluation of lymph node involvement may direct surgical decision-making during the procedure. An intraoperative, non-invasive imaging technique, such as ultrasound, capable of reliably identifying excised lymph nodes and describing their morphologic characteristics could prevent empty nodal packets, support a more selective and appropriate use of frozen section analysis, and favor a targeted lymphadenectomy focused on metastatic lymph nodes. However, the diagnostic performance of conventional ultrasound probes is limited by insufficient spatial resolution, particularly for small metastatic deposits. High-frequency ultrasound (HFUS) represents a relevant technological advance, providing markedly higher spatial resolution and allowing detailed evaluation of lymph node morphology in excised tissue. Based on this evidence, the aim of the present study is to evaluate the accuracy of a 33-MHz ultra-HFUS probe used intraoperatively on excised lymph node tissue from patients diagnosed with ovarian, cervical, endometrial, and vulvar cancers. In addition, this study provides a qualitative visual characterization of lymph node morphology through correlation with histopathological findings. Methods: A multicenter prospective observational study was conducted between June 2025 and December 2025 at the Fondazione Policlinico Universitario Agostino Gemelli IRCCS, Rome, Italy, and at Charles University and the General University Hospital, Prague, Czech Republic. Women with newly diagnosed or recurrent ovarian, endometrial, cervical, or vulvar cancer were consecutively included if scheduled for surgery requiring lymph node excision for staging or cytoreductive purposes. Overall, 100 patients and 374 lymph nodes were assessed intraoperatively ex vivo using a 33-MHz ultra-high-frequency linear ultrasound probe. Lymph nodes were classified according to the Vulvar International Tumor Analysis (VITA) consensus into five morphometric categories (LN1–LN5), with LN4 and LN5 considered sonographically metastatic. Diagnostic performance of HFUS was evaluated at both the patient and lymph node levels, using definitive histopathological examination as the reference standard. At the patient level, diagnostic performance of HFUS was compared with that of preoperative imaging for the detection of lymph node metastases. In addition, a qualitative imaging–histopathology correlation was performed through systematic comparison of HFUS images and corresponding histological slides in collaboration with expert pathologists. Findings: On a lymph node–based analysis, intraoperative ex vivo HFUS correctly classified 349 of 374 lymph nodes, yielding a sensitivity of 88.5%, a specificity of 94.1%, and an overall accuracy of 93.3%. On a patient-based analysis, intraoperative ex vivo HFUS demonstrated higher sensitivity than preoperative imaging for the detection of lymph node metastases (84.6% vs 57.7%), with lower specificity (87.8% vs 94.6%) and comparable overall accuracy (87.0% vs 85.0%). A qualitative imaging–histopathology correlation was also performed, allowing detailed visualization of lymph node morphology and its correspondence with histological findings. Interpretation: Our findings support HFUS as a promising intraoperative technique in gynecological oncology, achieving high diagnostic accuracy for the ex vivo detection of lymph node metastases and showing higher sensitivity compared with preoperative imaging at the patient level, thereby highlighting its potential clinical relevance. Further studies are warranted to better define its intraoperative role across different gynecological tumor types and nodal scenarios, ultimately supporting a more individualized surgical approach.