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

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

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

Workup

Imaging Studies

• Contrast-enhanced CT scanning helpful for determining the extent of tumor infiltration. Detection of grossly positive nodal disease, particularly when central necrosis is present, is enhanced with contrast-enhanced CT scans. The accuracy for detecting nodal metastases is reportedly improved from 70% to 93% when a physical examination is combined with CT scans, but occult disease can still be missed.
• Fluorodeoxyglucose-positron emission tomography is performed before removal of the primary tumor and/or dissection of the neck, and results are compared with those from histopathology studies. Fluorodeoxyglucose-positron emission tomography confirms the clinically identified location of the primary tumor site. Fluorodeoxyglucose-positron emission tomography shows promise in the initial staging of cancer of the head and the neck. It also provides additional accuracy to the conventional staging process using CT scans.
• MRI is beneficial for staging the size of the suggestive lymph nodes, for the evaluation of central lucency reflecting necrosis, for the assessment of irregular nodes with rim enhancement, for the evaluation of indistinct nodal margins, and for obliteration of fat or tissue planes.

Other Tests

Imaging studies are performed to detect any lymph node metastases. If the imaging studies fail to positively show lymph node metastases, a SLN biopsy is indicated for oral and oropharyngeal SCCs.

Histologic Findings

The current histopathologic routine is to step-section the SLNs at multiple levels and to perform immunohistochemical staining with S-100 protein and homatropine methylbromide to identify micrometastatic disease. If any question remains about abnormal cells after the first sections are taken, additional sections are obtained. Immunohistochemistry results identify an additional 10-20% of patients with positive SLNs, in whom micrometastases are not seen on routine sections stained with permanent hematoxylin and eosin (H&E). At least some of the increased rate of detection of micrometastatic disease is attributable to step-sectioning at multiple levels.

The approach for sampling involves bivalving the lymph node, fixing the 2 halves face down, and subsequently sectioning each half into 10 sections, which are alternately used for H&E staining, immunohistochemistry testing, and molecular staging. The sensitivity of intraoperative frozen section examination of the SLN is disappointingly low (<50%), although false-positive results are almost never reported. Because of concerns about tissue loss during the frozen section procedure, most centers eschew frozen sections and rely on permanent sections, except to confirm grossly suggestive metastatic disease.

Staging

Lymph node groups of the neck region are divided into 2 triangles, the anterior and the posterior triangles, which are further subdivided as follows:

• The anterior triangle of the neck is bounded (1) anteriorly by the median plane, (2) posteriorly by the sternocleidomastoid muscle, and (3) superiorly by the base of the mandible. Also, a line joins the angle of the mandible to the mastoid process. The apex of the triangle lies above the manubrium sterni. The anterior triangle is subdivided by the digastric muscle and the superior belly of the omohyoid into the submental triangle, the digastric triangle, the carotid triangle, and the muscular triangle.
  • The submental triangle is the median triangle. On each side, the boundaries are the anterior belly of the corresponding digastric muscles. Its base is formed by the body of the hyoid bone. Its apex lies at the chin. The floor of the triangle is formed by the right and left mylohyoid muscles, with the median raphe uniting them.
  • The digastric triangle boundaries are, anteroinferiorly, the anterior belly of the digastric; posteroinferiorly, the posterior belly of the digastric and the stylohyoid; and superiorly (base), the base of the mandible and a line joining the angle of the mandible to the mastoid process. The roof boundary is the skin, superficial fascia, and deep fascia. The floor is formed by the mylohyoid muscle anteriorly and by the hyoglossus posteriorly and anteroinferiorly.
  • The carotid triangle boundaries are, superiorly, the posterior belly of the digastric muscle and the stylohyoid; anteroinferiorly, the superior belly of the omohyoid; and posteriorly, the anterior border of the sternocleidomastoid muscle. The roof boundary is skin, superficial fascia, and an investing layer of deep fascia. The floor is formed by parts of the thyrohyoid muscle, the hyoglossus, and the middle and inferior constrictors of the pharynx. Most of the SLNs are found in the carotid or the digastric triangle.
  • The muscular triangle includes the superficial structures in the infrahyoid region. The boundaries are, anteriorly, the anterior median line of the neck from the hyoid bone to the sternum; posterosuperiorly, the superior belly of the omohyoid muscle; and posteroinferiorly, the anterior border of the sternocleidal mastoid muscle.
• The posterior triangle is a space on the side of the neck situated behind the sternocleidomastoid muscle. The boundaries are, (1) anteriorly, the posterior border of the sternocleidomastoid muscle; (2) posteriorly, the anterior body of the trapezius; and (3) inferiorly (base), the middle third of the clavicle. The apex lies on the superior nuchal line where the trapezius and sternocleidomastoid muscle meet. The posterior triangle is subdivided by the inferior belly of the omohyoid into the omohyoid triangle and the supraclavicular triangle. Lymph node dissection in both the triangles in the posterior compartment is considered to be the same level.

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