Society of Nuclear Medicine Procedure Guideline for Lymphoscintigraphy and the Use of Intraoperative Gamma Probe for Sentinel Lymph Node Localization in Melanoma of Intermediate Thickness

A. This guideline is written specifically for lymphoscintigraphy in patients with primary melanomas that originate in the skin. Staging of these tumors is based on tumor thickness (Breslow measurement) and level of skin invasion (Clark’s level), both of which are determined by the pathologist from a biopsy sample. Ample data correlate patient survival with Breslow and Clark measurements. In the past, elective lymph node dissection (ELND) of the lymphatic bed believed most likely to drain the primary tumor site (based on Sappey’s classic anatomic description of cutaneous lymphatic flow) was used as part of the staging procedure for melanoma. ELND has been a controversial staging procedure for patients with intermediate (I and II) stage melanoma, because approximately 80% have tumor-negative lymph nodes and therefore do not need ELND, a procedure associated with significant morbidity and cost. The sentinel lymph node excisional biopsy procedure, in contrast, is simpler and not associated with significant morbidity, provides accurate information about lymphatic drainage patterns, and allows the surgeon to make a smaller incision directly over the node, based on the image and probe counts. Lymphoscintigraphy images readily demonstrate the unpredictability of lymphatic drainage patterns. Sentinel lymph node biopsy, after identification by lymphoscintigraphy and excision using the intraoperative gamma probe and/or blue dye technique, is frequently performed in patients without either clinically apparent metastases or early intermediate-stage melanoma (Clark level <4; Breslow thickness 0.76–4 mm) because of its significant diagnostic and prognostic i n f o r m a t i o n . B. Definitions 1. Lymphoscintigraphy: Imaging pathways of lymphatic flow and lymph nodes after injection of a radiopharmaceutical that is absorbed by the lymphatics. 2. Sentinel lymph node: The first lymph node in a lymph node bed to receive lymphatic drainage from a tumor. Often drainage to more than 1 lymph node group and sentinel node is identified. 3. Blue dye technique: Intraoperative injection (usually peritumoral) of isosulfan blue dye for the purpose of staining lymphatic vessels and sentinel lymph nodes so that they can be identified visually during surgery for excisional biopsy. 4 . Gamma-detecting intraoperative probe: Small, hand-held radiation-detecting device that uses auditory signals and meter read-outs of counts detected. The intraoperative gamma probe can be used effectively by the surgeon and nuclear medicine physician as a guide to find the radiolabeled sentinel lymph node(s). Society of Nuclear Medicine Procedure Guideline for Lymphoscintigraphy and the Use of Intraoperative Gamma Probe for Sentinel Lymph Node Localization in Melanoma of Intermediate Thickness