Sentinel Lymphadenectomy in Patients Diagnosed With Cervical Cancer
Achim Schneider
Christhardt Köhler
GENERAL PRINCIPLES
Definition
In patients diagnosed with cervical cancer, sentinel lymphadenectomy (LNE) refers to the retrieval of specific lymph nodes (LNs) which have the highest risk to contain metastasized tumor cells. By injecting specific markers such as radioactively labeled (using technetium, Tc) albumin or dye such as Patent Blue V or Indocyanine green (ICG) into the site of the primary tumor, the marker is transported via lymphatic vessels to the first draining LN which is called the sentinel lymph node (SLN). In cervical cancer, this SLN is usually located in the pelvic area along the pelvic vessels bilaterally. The SLN is located at the bifurcation of the iliac vessels in about two-thirds of patients. The SLN technique is most beneficial in patients with squamous- or adenocarcinoma with a diameter of less than 2 cm. Preferential harvesting is performed laparoscopically for easier identification and reduction of intra- and postoperative morbidity for the patient. In contrast to traditional systematic LNE, patients “lose” only a few LNs and the pathologist is confronted with a limited amount of tissues with the highest risk of containing tumor cells which can be analyzed meticulously using serial sections and markers specific for tumor cells originating from cervical cancer. This increases oncologic safety and decreases intra- and postoperative morbidity for the patient.
Differential Diagnosis
Detection of the SLN can be difficult if not only one but several LNs have been labeled on each pelvic side. The LN station next to the SLN is called the second echelon LN which can be difficult to differentiate from the SLN, since radioactive signals or color staining can be of similar intensity as for the SLN.
Anatomic Considerations
The SLN at the junction of the internal and external iliac artery is usually easy to identify. Laparoscopic surgery is ideally suited to reach this goal: 7× magnification and bloodless dissection are the hallmarks of this technique and prerequisites for easy identification. In one-third of patients, the SLN locates in areas which can be difficult to access, such as close to the cervix, at the iliac-uterine junction, or in the presacral or lower paraaortic area. However, for surgeons who are familiar with the pelvic anatomy, SLN LNE is an easy operation.
IMAGING AND OTHER DIAGNOSTICS
When Tc-based radioactive labeling is used for detection of the SLNs, preoperative scintigraphy should be performed. The scan is taken 60 minutes following application and usually shows two hot spots on each side of the pelvis. In addition, single portal emission computed tomography (SPECT) can be used for more precise localization of the targets. A preoperative scan can be useful for the surgeon and may allow easier and quicker intraoperative detection, especially in patients where the sentinel node is not located medial to the common iliac bifurcation. However, SLNs close to the cervix will not show up at the scan since the intracervical signal from the injection site is too strong and incorporates the SLN signal. Intraoperative detection is done by inspection of the SLN with the strongest color uptake if dye has been used as marker. A gamma probe is used to detect Tc-labeled LNs. Probes are available for open and laparoscopic surgery. The SLNs are sent for frozen section and analyzed using hematoxylin staining. On paraffin-embedded tissue, serial sections are taken and stained with hematoxylin-eosin and markers such as p16, Ki-67, stathmin 1, and pancytokeratin in order to detect micrometastasis between 0.1 and 1 mm in size. Disseminated tumor cells can be identified when RNA of the respective HPV type of the primary tumor is found in the SLN. The false-negative rate of SLN analysis is 10%, which means that in 100 patients with cervical cancer of tumor size not larger than 20 mm, 10 patients are N1 and one of these patients will have a false-negative result, but 84 patients will have been spared from systematic LNE (See Table 19.1). Thus, safety of 1 patient has to be weighed against morbidity in 84 patients when informed and participating patient’s consent is requested.
Preoperative MRI or PET scan can be performed in order to exclude major metastatic disease in the LNs. However, debulking of LNs is part of the modern concept for patients who undergo primary chemoradiation due to metastatic disease in LNs. Thus, enlarged LNs on imaging will not exclude the patient from laparoscopic staging. Therefore, imaging techniques have only limited value prior to planned SLN LNE.
PREOPERATIVE PLANNING
The patient is counseled about the extent of the operation, which is equivalent to a conventional operative laparoscopy with four incisions or alternatively one single-port incision.
If radioactive labeling is used, the patient is informed about the side effects of Tc. If blue dye is applied, patient and potential visitors must be informed that the color of the patient’s skin and urine will be blue green stained for up to 24 hours postoperatively. The patient is also informed that an allergic reaction to Patient Blue V may occur.
There should be no contraindication against CO2 gas-supported laparoscopy, such as poor general condition or herniation of the diaphragm.
Tumor diameter of no more than 2 cm should be confirmed.
In case of lack of detection of an SLN, the patient should be informed and consent to a systematic complete pelvic uni- or bilateral LNE.
In case of tumor-involved LNs, the patients should be informed about and consent to a systematic complete pelvic bilateral and paraaortic LNE.
No specific preoperative preparation such as bowel prep, central line, or antibiotics are necessary for laparoscopic SLNectomy.
Urinary catheter.
Nasogastric/orogastric tube.
Availability of frozen section.
For SLN labelling and detection:
Preoperative Preparation
Obesity does not interfere with this type of surgery if LNectomy does not have to be extended outside of the pelvis. If SLNectomy is to be combined with radical vaginal trachelectomy (RVT) or nerve-sparing laparoscopic vaginal radical hysterectomy, the preoperative regimen is modified according to the demands of these surgeries.
Patients with abdominal incisions from previous surgeries or status post intra-abdominal and/or pelvic infections and risk for adhesions are counseled for additional incisions (e.g., subcostal) and risk for injury of abdominal organs such as bowel, bladder, ureter, and/or vessels. Also, the very unlikely conversion to open surgery is mentioned.
SURGICAL MANAGEMENT
Positioning
The patient is placed in a 15- to 30-degree Trendelenburg position with closed legs and arms tucked to the body. A peripheral line is sufficient. The entire abdominal wall is prepped and draped such that the area from symphysis to the xiphoid is accessible. A nasogastric tube and a peripheral venous access are placed.
Operating Room Setup
Supine position
Extended legs
Use belts and/or shoulder support
PROCEDURES AND TECHNIQUES
Sentinel Lymphadenectomy (Video 19.1) 
