Radar-guided localization system for accurate resection of selected cervical lymph nodes

Abstract

Needle biopsy of cervical lymph nodes is a common method to diagnose metastasis. Excisional biopsy is typically reserved for cases where needle biopsy is nondiagnostic, usually due to sampling error or insufficient cellular material. Locating the target lymph node in the neck can be difficult. A radar-guided localization (RGL) system may overcome this. A 41-year-old man presented with recurrent papillary thyroid carcinoma in the thyroid bed and radiologically suspicious lateral cervical lymph nodes on positron emission tomography–computed tomography. Repeated needle biopsies failed to confirm metastasis in these nodes. A reflector was inserted preoperatively into a lateral cervical lymph node under ultrasound guidance and local anaesthesia, enabling its precise intraoperative identification several weeks later. The node was successfully localized and removed at the time of surgery with minimal dissection of the surrounding tissues. RGL is a wire-free, nonradioactive localizer that facilitates accurate intraoperative identification of small, nonpalpable lymph nodes in anatomically complex areas such as the neck. The reflector can be placed in the target node at any time prior to surgery and may overcome the limitations of conventional localization techniques to improve surgical precision and outcomes in head and neck oncologic surgery.

Introduction

Excisional biopsy of neck lymph node, when indicated, can be challenging for nonpalpable nodes in complex neck anatomy. The dense distribution of cervical lymph nodes, neurovascular structures along with aesthetic considerations, further complicates surgical excision in the absence of precise intraoperative localization.

The SCOUT RGL system by Merit Medical (Jordan, UT), comprises a reflector, console, and handpiece, providing audible and visual feedback, as well as real-time measurements of the distance between the probe and reflector, for precise intraoperative localization. The SCOUT reflector has United States Food and Drug Administration (FDA) approval for localizing nonpalpable breast and other soft tissue lesions [1]. More recently, SCOUT has been used for intraoperative localization of pulmonary nodules [2], axillary lymph nodes [3], musculoskeletal mass [4], and melanoma lymph node metastasis [5].

Here, we describe the first known application of the SCOUT RGL system for intraoperative localization and navigation during excisional biopsy of a targeted lateral cervical lymph node in a patient with recurrent papillary thyroid carcinoma.

Case report

A 41-year-old man with a history of tall-cell variant papillary thyroid carcinoma (PTC) underwent total thyroidectomy with left central compartment (Level VI) lymph node dissection, followed by radioactive iodine (I-131) ablation 7 years earlier. A rise in thyroglobulin levels prompted a fluorodeoxyglucose positron emission tomography (FDG PET) scan, which revealed multiple FDG-avid lymph nodes in the left Level II, III, and VI (Fig. 1). He was found to have biopsy-confirmed recurrent PTC in the left paratracheal region (Level VI). However, despite multiple ultrasound-guided fine-needle aspiration attempts of the FDG-avid lateral neck nodes, cytology remained negative for metastatic disease. The patient was reluctant to undergo a lateral neck dissection without histological confirmation of metastasis.

An excisional biopsy of the FDG-avid lymph node with intraoperative frozen section analysis was planned. If metastatic disease was confirmed, a lateral neck dissection and completion paratracheal dissection were to be performed during the same operation.

Intraoperative identification of the FDG-avid lateral neck lymph node was anticipated to be challenging. To minimize unnecessary skin incisions and tissue dissection, we proposed using the SCOUT RGL system. At the time, no published reports were available on its use for cervical lymph node localization in thyroid cancer. After consultation with the manufacturer, we selected the SCOUT Mini Reflector (8 mm) for this purpose.

With informed consent, the SCOUT reflector was placed under ultrasound guidance and local anaesthesia in sterile conditions about one week before surgery. The device was tested and confirmed to be functional. The patient tolerated the procedure well and was discharged home. Placement of a reflector in level VI was considered but ultimately avoided due to the theoretical risk of injury to the recurrent laryngeal nerve. A few days later, the patient developed symptomatic respiratory infection and tested positive for COVID-19. As a result, the surgery was postponed and rescheduled 48 days after the initial reflector placement.

At surgery, the SCOUT system successfully localized the previously marked lymph node (Supplementary Video 1). A small skin incision was made, and real-time navigation was used to guide dissection along the posterior border of the sternocleidomastoid muscle. With anteromedial retraction of the muscle and continued SCOUT-guided dissection, two small lymph nodes were identified anteromedial to the internal jugular vein. They were located adjacent to each other, with the reflector positioned between them. Both nodes were excised, with the larger measuring ~6 mm (Fig. 2). Frozen section analysis confirmed metastatic disease, prompting completion of a lateral neck dissection followed by revision of the Level VI dissection.

Discussion

We described a novel use of the SCOUT RGL system to precisely localize a target lymph node in the neck. This method facilitated an intraoperative excisional biopsy, days after the implementation of the reflector, through a small skin incision with minimal tissue invasion and helped with the decision to perform the appropriate surgery and better outcome.

125- I radioactive seed [6] and image guided wire localization of lymph nodes in the neck [7, 8] and wire localization of the recurrent thyroid cancer [9] have been described in the literature before.

SCOUT RGL systems may avoid many of the challenges associated with other localization techniques. As demonstrated in our case, radio-reflector placement and the subsequent surgical procedure can be performed independently, with several weeks in between if necessary. Decoupling of radiology and surgery schedules will reduce delays on the day of surgery, increase procedural scheduling flexibility which may help alleviate the anxiety and stress often associated with traditional localization methods. Wire-free localization provides surgeons with greater flexibility in selecting the optimal surgical approach and potentially improving surgical outcomes. Finally, unlike radioactive seed localization, SCOUT does not involve the risks or regulatory issues associated with handling radioactive materials [10].

Radar-reflector guided surgery has the potential to play a greater role in head and neck oncologic procedures in the future.

Acknowledgements

We thank the patient for consenting to have his case presented in this report. We also acknowledge the operating theatre and radiology staff at Westmead Hospital, the SCOUT representatives for their support as well as Dr. Laila Parvaresh for her contribution to review and editing of the manuscript. The work was carried out at Westmead Hospital, Cnr Hawkesbury Rd & Darcy Rd, Westmead, NSW 2145, Australia.

Conflicts of interest

None declared.

Funding

None declared.

Ethics and integrity statement

Patient consent was obtained for the publication of this case report through the Western Sydney Local Health District ethics approval process. No funding was received for this work, and the authors declare no conflicts of interest. All procedures were conducted in accordance with relevant ethical guidelines.

References