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From the Department of Surgery, Division of Breast Surgical Oncology, University of Arkansas for Medical Sciences, Little Rock, Arkansas.
Correspondence: Address correspondence to: V. Suzanne Klimberg, MD, Department of Surgery, Division of Breast Surgical Oncology, University of Arkansas for Medical Sciences, 4301 West Markham #725, Little Rock, AR 72205; Fax: 501-526-6191; E-mail: klimbergsuzanne{at}uams.edu
Surgical staging of the axilla in breast cancer, one of the most important predictors of patient survival, is the gold standard for assessing axillary lymph node involvement.1,2 Sentinel lymph ode (SLN) biopsy is fast replacing the level I-II axillary lymph node dissection (ALND), which in the 1980s replaced the level I-III dissection.3,4 It is hoped, a noninvasive way to determine lymph node involvement will soon be available.
No good preoperative way exists to assess lymph nodes. Although an article can always be found to support a view of the superiority of a technique, most techniques are about 70% accurate in terms of telling whether an axilla holds a tumor-bearing lymph node or not. Palpation, mammography, ultrasound (US), positron emission tomography (PET), magnetic resonance imaging (MRI), and sestamibi imaging are more or less equally accurate at determining nodal status.5–7 In fact, Bedrosian et al.8 state that US has become the primary imaging modality for determining the status of the regional lymph nodes. In their series, however, two thirds of patients with nodal disease found US negative had metastatic foci <5 mm. US is inexpensive and more readily available for assessing the patient for metastases. Perhaps it is also better in the patient with a palpable node who has not had a prior excisional breast biopsy. Nonetheless, it remains clear that US can not assess nodal negativity, which is what we would all like to say to spare the patient unnecessary surgery. The negative predictability of this study was 78%. Palpation is still the primary technique of assessment and seemingly just as accurate as any other preoperative examination. Having said that, in the Bedrosian et al.8 study, the calculated negative predictive value for the overall group of patients would have been just the same as if one had just predicted every one was negative from the outset without any preoperative examination.
Internal mammary lymph node localization during a SLN procedure is difficult and at times uncertain; perhaps, as a result of this, its value has been heavily debated.9 In our hands, if there appears to be a SLN hot spot in the medial chest wall, US is used to confirm a retrievable lymph node along the internal mammary artery. If the lymph node is not identifiable by US we do not explore. Here, we are not trying to detect metastases by US but using US to enhance our vision. If the lymph node cannot be seen by US, then it will not be seen grossly.
A more exacting way must be found to define nodal positivity other than by size (>1 cm), roundness, and disruption of internal echoes. A few studies have looked at what is called the roundness factor, surface area, blood flow, and contrast enhancement.10 US has really blossomed in the last decade from a tool to only discern solid from cystic masses to one with fairly high accuracy in discriminating benign from suspicious lesions. So, too, will our understanding of what a cancerous node looks like on US advance.
The real value in US is to complement the physical examination and to guide biopsy of clinically suspicious axillary lymph nodes. Of patients in the Bedrosian8 study, 93 were excluded from data analysis because they received preoperative chemotherapy, presumably for advanced disease or palpable lymph nodes. SLN localization after chemotherapy, which is successful in only about 80% of patients, carries a high false–negative rate.11 Are we so inaccurate with palpation and US that all patients should have SLN only before chemotherapy? This paradigm would allow the medical oncologist to proceed with accurate knowledge and help spare the patient a full axillary node dissection after chemotherapy if the SLN is negative.
Currently, US is most helpful in clinically positive nodes or in clinical scenarios such as large or locally advanced primaries where the risk of a positive node is high. Negative predictability, however, is too low to solely rely on US, even when coupled with fine needle aspiration. Future endeavors at fine tuning US resolution, new detection methods, or new percutaneous whole lymph node retrieval devices will help in minimally invasive staging of lymph nodes.
Received for publication September 23, 2003. Accepted for publication September 23, 2003.
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