Lymphatic Mapping of the Breast: Locating the Sentinel Lymph Nodes

Abstract

When the concept of sentinel lymph node biopsy was described in patients with melanoma, researchers quickly started to use lymphatic mapping techniques in breast cancer patients in an attempt to locate the sentinel node in the axilla. We have been performing mammary lymphoscintigraphy in this role for 6 years and have now studied 159 patients. Like others, we have found that most breast cancers (93%) have lymphatic drainage that includes the axilla, and we have found an average of 1.4 axillary sentinel nodes in these patients. Surgical biopsy of the axillary sentinel nodes accurately staged the node field in 96% of patients. We have also found, however, that the pattern of lymphatic drainage from the cancer site is unpredictable; and in 49% of patients lymphatic drainage occurred across the center line of the breast to axillary or internal mammary sentinel nodes. In more than half of our patients (56%) lymphatic drainage occurred to lymph nodes outside the axilla including the internal mammary (45%), supraclavicular (13%), and interpectoral and intramammary interval nodes (12%). These nodes are also sentinel nodes, and their presence indicates that a sentinel node biopsy procedure that stages only the status of the axillary lymph nodes has the potential to understage about half the patients with breast cancer. High quality lymphoscintigraphy allows accurate mapping of peritumoral lymphatic drainage in most patients with breast cancer. It is possible that in the future accurate nodal staging in each individual will involve biopsy of all sentinel lymph nodes, regardless of their location.

Lymphatic drainage of the skin

“…1 Usually, four injections of 5 to 10 MBq (0.05 to 0.1 mL/injection) are used, although this will depend on the primary melanoma size. After tracer injection, dynamic imaging is performed to follow the lymphatic collecting vessels until they reach the draining SNs.…”

“…It is decreased by cold, lack of movement, and external pressure. 1 During LS the patient must be kept warm to encourage movement of the radiocolloid or blue dye, and massage can be a very useful intervention to enhance flow. Even light external pressure dramatically reduces lymph flow and should be avoided.…”

“…1 An SN is not just the first node seen on dynamic imaging, because there may be multiple separate lymph channels that have different rates of lymph flow. If they drain to different nodes, these are all SNs, regardless of the time taken for the lymph containing the radiocolloid to reach them.…”

“…The pursuit of this goal has led to the discovery of several new lymphatic drainage pathways from the skin. [1][2][3][4][5] Several factors are critical for an accurate map of lymphatic drainage.…”

Evaluation of the subtraction method utilizing posterior view for improving visibility of the sentinel lymph nodes for lymphoscintigraphy in breast cancer

“…Most facilities use preoperative lymphoscintigraphy to localize SLNs in patients with breast cancer. In breast cancer cases, lymphoscintigraphy reveals drainage from the tumor to axillary lymph nodes and accurately localizes SLNs within the body, thus providing surgical assistance [2][3][4][5][6]. Currently, lymphoscintigraphy is the standard means of evaluating SLNs from tumors.…”