eMedicine Specialties > Otolaryngology and Facial Plastic Surgery > Head & Neck Surgery

Sentinel Lymph Node Biopsy in Patients With Squamous Cell Carcinoma: Treatment

Author: Amit Dwivedi, MD, Assistant Professor of Surgery, University of Louisville
Coauthor(s): Karl J D'Silva, MD, Fellow in Hematology/Oncology, Department of Internal Medicine, Breslin Cancer Center, Michigan State University; Nafisa K Kuwajerwala, MD, Staff Surgeon, Breast Oncology, William Beaumont Hospital; Thabet Abbarah, MD, FACS, Consulting Staff, Department of Otolaryngology, North Oakland Medical Centers
Contributor Information and Disclosures

Updated: May 22, 2008

Treatment

Preoperative Details

Patients undergo lymphoscintigraphy up to 1 day prior to surgery. A maximum of 40 MBq^99m Tc-labeled human serum albumin (ie, AlbuRES, Nanocoll) is injected throughout the normal mucosa surrounding the tumor edge and the submucosa on the deep aspect of the tumor in a volume of approximately 0.5-1 mL. A syringe with a permanently secured needle is used for injection, thereby preventing inadvertent spillage of colloid into the mouth. Colloid is injected at as many points as necessary in an attempt to completely surround the tumor. A mouthwash is used immediately following injection to prevent pooling or swallowing of residual radioactive material by the patient.

Static lymphoscintigraphy is performed at 15 minutes, 30 minutes, and 1 hour postinjection in 2 planes or until the appearance of radioactive nodes. Hot spots are usually seen 15 minutes postinjection. If nodes are still absent 1 hour after injection, the lymph nodes are too close to the injection site or radiocolloid has leaked out of the injection site.

Either a cobalt Co 57 marker is used to trace the patient outline or a flood source of⁵⁷ Co or^99m Tc is placed behind the patient to produce a silhouette of the patient outline. In light of the radiation dose, the marker pen is preferable. A gamma camera fitted with a low-energy, general-purpose collimator is used to acquire images of the patient. A 20% window centered on the 140 keV photopeak is selected, and the camera is interfaced to a suitable computing system. The locations of radioactive lymph nodes are marked on the patient's skin, the position of a⁵⁷ Co solid-source pen is observed on the camera's persistence display, and the pen is moved until its position overlies a radioactive node. This position is then marked on the patient's skin using indelible ink. During the skin marking, a lead plate of an appropriate thickness (eg, 3 mm) is used to shield the injection site.

Following image acquisition, a software mask is applied to all images to eliminate radioactivity from the injection site. A region of interest, drawn around the image of the site of injection, is used as the basis for the mask applied.

Two colloids are commonly used for lymphoscintigraphy: AlbuRES and Nanocoll. AlbuRES has a mean particle size of 500 nm and is a slower-moving particle that remains in first-echelon (sentinel) nodes but requires a high density of terminal lymphatic vessels at the injection site. For these reasons, AlbuRES is the colloid of choice on the tongue and on the floor of the mouth. Nanocolloid has a mean particle size of 50 nm and is a faster-moving colloid, which finds lymphatic vessels despite injection into tissues with low densities of terminal lymphatics. Nanocolloid also moves readily from sentinel nodes to subsequent-echelon nodes. For these reasons, nanocolloid is the colloid of choice for primary tumors that are not located on the floor of the mouth or on the tongue. Record the choice of colloid.

The overall success rate of a SLN biopsy by blue dye is 82%, by radioactive mapping is 94%, and by a combination of both is 98%.

Intraoperative Details

At operation, 1-2 mL of Patent Blue V dye may be used. To approximate the same injection sites as for radiocolloid, ensure that the same person performs all the injections. A suitable incision is made in the neck in such a position as to facilitate excision of the incision scar if a subsequent neck dissection is necessary.

The handheld gamma probe is used to identify radioactive sentinel nodes, including those marked preoperatively during lymphoscintigraphy. To reduce detection of radiation from the injection site, a series of malleable, sterilized lead plates may be used to mask the injection site, thus aiding in vivo identification of radioactive nodes. Radioactive nodes are excised, and radioactivity within the node is confirmed ex vivo.

If the blue dye is used, stained lymphatics, if seen, are followed to the first draining lymph node, which is then harvested. Sentinel nodes are labeled according to their color and radioactivity. The anatomic neck level of the sentinel nodes is noted. Although sentinel nodes are usually harvested prior to treatment of the primary tumor, the proximity of the sentinel node to the injection site may require a further search for sentinel nodes following excision of the primary tumor. If sentinel nodes are sought after excision of the injection site, the nodes are not likely to be stained blue.

Because of the relatively high radioactivity present in the injection sites and the proximity to the sentinel node, detection of scattered radiation must be avoided as far as possible. In addition to the use of the lead plates described above, the gamma probe must have a well-collimated detector, which excludes gamma radiation except over a small angle in front of it. Set the pulse-height analysis window to only include the^99m Tc photopeak with a cutoff on the low-energy side at approximately 130 keV. Check the calibration at regular intervals of not more than 1 month (depending on the make and model of the instrument). Devise a quick check of calibration, and perform this quick check before each use. Calling on appropriate scientific or technical assistance may be necessary to ensure that the gamma probe is at its optimal settings and to make an estimate of its sensitivity at these settings.

Sentinel nodes are fixed in 10% neutral, buffered formalin, and, after fixation, they are bisected through the hilum (if identifiable) or through the long axis of the node. If the halves are thicker than 2 mm, the slices are further trimmed to provide additional blocks of 2 mm. If sentinel nodes are found to be free from tumor after the initial histologic examination, step-serial sections are prepared at an additional 6 levels in the block at intervals of approximately 150 µm. One H&E-stained section is prepared at each level. If the nodes still appear negative after histologic examination, an adjacent section from each level is examined by immunocytochemistry using the multicytokeratin antibody AE1/AE3.

The interpretation of the histopathology and immunocytochemistry results for the SLN is categorized as follows:

• Pathology code description
  • Stage 1: The sample is positive for tumor upon first examination using H&E stain.
  • Stage 2: The sample initially appears negative for tumor, but it is noted to be positive for tumor upon examination of the H&E stain of step-serial sections.
  • Stage 3: The sample is negative for tumor at stages 1 and 2 but positive for tumor based on immunohistochemistry results. To be categorized as positive for tumor, cells must be present that are (1) positive based on immunocytochemistry results and (2) cytologically observed to be nucleated cells with the characteristics of viable epithelial cells in both the immunocytochemical preparation and the serial H&E-stained sections. Cytokeratin positivity lacking the cytological features of viable tumor cells is categorized as stage 4.
  • Stage 4: Cytokeratin positivity does not show the features of viable tumor cells. This positivity likely represents either dying tumor cells (possibly apoptotic cells), characterized by eosinophilic bodies lacking normal nuclei, or macrophages with phagocytosed tumor products. Usually, these cells are single and not in small, cohesive groups. The decision to allocate nodes to this category requires careful comparison of the serial H&E-stained section and the immunocytochemical preparation.
  • Stage 5: The sample is negative for tumor at all stages.

If any lymph node contains a viable tumor (ie, stages 1-3 according to the pathology code description) either based on routine histology studies or based on immunohistochemistry and multiple sectioning, the patient undergoes a radical or modified radical dissection of the neck. Perform the dissection of the neck within 4 weeks of the SLN biopsy, and begin any adjuvant radiotherapy within 6 weeks of the dissection. Do not administer radiotherapy prior to a neck dissection.

For tumors in stage 4 or 5 according to the pathology code description, no further treatment to the neck is required and no prophylactic neck radiotherapy or additional surgery is necessary.

Postoperative Details

The current treatment for patients with SCC includes a proper diagnosis based on a high level of consideration and examination, with subsequent staging and development of a treatment paradigm. A treatment program of surgery, radiation, or chemotherapy is best developed by an oncology team that includes surgeons, radiation and medical oncologists, and rehabilitative specialists who all have significant experience in the care of patients with cancer involving the head and the neck. By using this approach, new protocols and surgical options can be appropriately offered to those patients with advanced cancers.

Follow-up

Patients are seen every 3 months for the first year, every 4 months for the following 2 years, and every 6 months until 5 years following a SLN biopsy. At any stage, if nodal disease is detected, patients can elect to undergo surgical treatment of the neck.

For excellent patient education resources, visit eMedicine's Cancer and Tumors Center. Also, see eMedicine's patient education articles Skin Cancer, Skin Biopsy, and Cancer of the Mouth and Throat.

Complications

Allergic reactions to isosulfan blue, nerve injury, lymphedema, neuropathy, fat necrosis, seroma, and hematoma can result following dissection of an SLN.

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