Objectives/Hypothesis Sentinel lymph node biopsy is a minimally invasive method to stage the regional lymphatics that has revolutionized the management of patients with intermediate-thickness cutaneous melanoma. Head and neck surgeons have been encouraged by the accuracy of sentinel lymph node biopsy in cutaneous melanoma and have applied the technique to patients with head and neck squamous cell carcinoma (HNSCC). The objectives of the study were 1) to study the feasibility and accuracy of sentinel lymph node biopsy as a method to stage the regional lymphatics in HNSCC and 2) to determine whether there are qualitative differences between the cutaneous and mucosal lymphatics that would affect the technique used in HNSCC.
Study Design Two methods of investigation were employed: a prospective laboratory study using a feline model for sentinel lymph node biopsy and a retrospective review of patients who received lymphoscintigraphy before neck dissection and intraoperative identification of the sentinel lymph node.
Methods Lymphoscintigraphy and a gamma probe were used in four felines to study the kinetics of technetium-labeled sulfa colloid (Tc-SC) in the mucosal lymphatics. In the second part of the feline study, eight subjects were studied intraoperatively. Tc-SC and isosulfan blue dye were used to study the injection technique for the mucosal lymphatics and to determine the time course of the dye and Tc-SC to the sentinel lymph node. In Part II of the present study, a retrospective review of 33 patients with HNSCC was conducted. Twenty patients (stage N0) whose treatment included elective neck dissection were studied with preoperative lymphoscintigraphy and underwent intraoperative identification of the sentinel lymph node to determine the accuracy and feasibility of sentinel lymph node biopsy. Eight patients with palpable neck disease and five patients with recurrent or second primary disease whose previous treatment included neck dissection were also studied with lymphoscintigraphy before neck dissection.
Results In the feline study, both Tc-SC and isosulfan blue dye traversed the lymphatics rapidly, appearing in the sentinel lymph node in less than 5 minutes. Modification of the injection technique used for cutaneous melanoma was required to depict the sentinel lymph node of the base of tongue. In the human study, the sentinel lymph node was accurately identified in 19 of 20 (95%) N0 patients. On average, 2.9 sentinel lymph nodes (range, 1–5) were identified in 2.2 (range, 1–4) levels of the neck. Sentinel lymph nodes were bilateral in 4 of 19 patients. When the sentinel lymph node was identified, it accurately predicted the pathological nodal status of the regional lymphatics. Three of 20 patients had cervical metastases, and the sentinel lymph node was identified in 2 of 3 patients with pathologic nodes (pN+). Focal areas of radiotracer uptake were identified in seven of eight patients with palpable disease. These areas corresponded to the level with palpable disease in four patients. The lymphatics delineated by lymphoscintigraphy in the five patients with previous neck dissection were outside the levels that had been dissected. Lymphoscintigraphy depicted collateral patterns of lymphatic drainage.
Conclusions Sentinel lymph node biopsy is technically feasible and is a promising, minimally invasive method for staging the regional lymphatics in patients with stage N0 HNSCC. Lymphoscintigraphy alone may determine the levels that require treatment in patients with disrupted or previously operated cervical lymphatics.