Breast cancer is the most common malignancy diagnosed in women in North America. It is reported that one in seven women will develop this malignancy during her lifetime. Based on current statistics, about 420,000 women per year will develop this disease over the next decade and approximately one third of all patients diagnosed with breast cancer will die from this malignancy.
The surgical management of breast cancer keeps evolving toward minimally invasive surgery. About 100 years ago, the surgical treatment of choice was radical mastectomy; 50 years later modified mastectomy was introduced and today many patients undergo a lumpectomy without compromising their prognosis. The status of the regional lymph node basin is one of the most important prognostic factors of survival. The presence of regional axillary lymph node metastasis decreases 5–year survival by 28–40% [1, 2]. The surgical management of patients with invasive breast cancer is a particularly controversial area. Only a few years ago all patients with invasive breast cancer would routinely undergo complete axillary lymph node dissection (ALND). This aggressive approach was justified by the need for local control of the disease and the need for vital information regarding metastatic involvement of the axillary lymph nodes; information regarding involvement of the axillary lymph nodes would determine the need for adjuvant chemotherapy. Multiple studies have reported, however, that only 20% of all patients undergoing ALND will in fact have metastatic involvement of the axillary area. In addition, ALND is reported to be associated with significant postoperative morbidity such as lymphedema involving the extremity, wound infections, seroma and drain discomfort, paraesthesias, and painful neuromas [3]. Thus, there was an urgent need for an alternative approach that would limit the indications for ALND.
In the early 1990's, it was suggested that lymphoscintigraphy and selective lymphadenectomy could be used for the management of this group of patients [4, 5]. Lymphoscintigraphy is a procedure performed to outline the lymphatic drainage of primary tumors using radiopharmaceuticals [fig. 1]. While in the past lymphoscintigraphy has been used for the management of malignant melanoma, more recently this modality has been adapted for identification of the first lymph node to drain tumor cells in patients with metastatic breast cancer (sentinel node). Lymphatic mapping of primary breast tumors with a radiopharmaceutical can be done to identify the sentinel node(s), and selective lymphadenectomy can be performed under local anesthesia. One or two sentinel nodes are then submitted for detailed pathologic examination, including immunohistochemistry and special stains designed to find micrometastases. This allows for more precise staging. As a result, only a fraction of patients with invasive breast cancer who undergo a sentinel node biopsy and are found to have metastatic involvement of this node will eventually undergo ALND.
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Figure 1. Lymphoscintigraphy of the right breast tumor showing the lymphatic drainage to two axillary nodes.
Procedure
Radiopharmaceutical: 450–500 uCi Tc–99m sulfur colloid filtered to 0.2 microns diluted in normal saline to 6 cc.
Route: Via breast tissue in 6 equal injections around the primary mass or biopsy site.
Imaging: Gamma camera. Static images 3 minutes per view until lymphatic pathway or a lymph node is visible. The body contour should be outlined with the marker or, alternatively, a transmission image could be made.
Intraoperative: A portable gamma probe is used to identify the sentinel node allowing surgical excision.
