Lymphoscintigraphy Overview Background

Lymphoscintigraphy Overview Background Lymphoscintigraphy (sentinel lymph node mapping) is an imaging technique used to identify the lymph drainage basin, determine the number of sentinel nodes, differentiate sentinel nodes from subsequent nodes, locate the sentinel node in an unexpected location, and mark the sentinel node over the skin for biopsy. Sentinel node mapping is rapidly becoming an alternate staging procedure for the axilla in managing early breast cancer.[1] Several well-conducted studies have provided high-quality evidence for its usefulness.[2] Sentinel node scanning was initially studied in cutaneous melanomas to detect lymphatic drainage patterns prior to surgery. The procedure is applicable to almost all regions of the body, but the greatest impetus to the technique came with the application of the procedure to identify breast sentinel nodes. The sentinel node is the first node to receive metastatic deposits in a malignancy. Lymphoscintigraphy is an important procedure because if the sentinel node is free of metastasis, subsequent nodes are also likely to be free of disease. The sentinel node is generally defined as follows: The node closest to the primary lesion The node with a radioactive channel leading to it The node with the highest count rate on lymphoscintigraphic imaging and probe counting The first node visible on lymphoscintigraphic imaging The blue node on dye injection technique The node with a blue channel leading to it Lymphoscintigraphy allows the patient to avoid axillary clearance surgery (axillary lymph node dissection) if the sentinel node is negative for metastatic disease. Given the high prevalence of breast cancer worldwide, the possibility of avoiding axillary clearance surgery in a significant number of patients makes this an extremely valuable procedure. This topic is limited to lymphoscintigraphy in breast cancer. Applications for malignant melanoma will be introduced, but a detailed discussion is beyond the scope of this article. Both radionuclide and nonradionuclide methods (blue-dye methods) will be discussed. Indications Lymphoscintigraphy is indicated for proven palpable or nonpalpable invasive breast carcinoma for which removal of the primary tumor and axillary node dissection would be indicated.[3] Contraindications Absolute contraindications to lymphoscintigraphy include clinically positive (N1) axilla and allergy to component used.[1] Relative contraindications to lymphoscintigraphy include the following[4] : Prior biopsy (especially excisional biopsy) Previous breast and axillary surgery Advanced disease (associated with fatty degeneration of nodes with reduced function) Neoadjuvant chemotherapy Multicentric and multifocal disease Ductal carcinoma in situ High body mass index and old age Pregnancy Surgeon’s experience and skills Other Applications Lymphoscintigraphy has become widely accepted in several other applications besides breast cancer,[5, 6] including malignant melanoma (stage I and II disease). Tc 99m tilmanocept is also approved for intradermal or SC injection for melanoma mapping.[7] The Multicenter Selective Lymphadenectomy Trial concluded that sentinel node scanning is a low-morbidity procedure for evaluating the regional nodal basin in early melanoma and should become the standard of care.[8] Other applications include head and neck cancer, thyroid cancer, non–small cell lung cancer, gastric cancer,[6] penile cancer,[9] and vulvar cancers.[10