Identification of the Sentinel Node by Ultrasonography in Patients with Breast Cancer

Background

Identification of the sentinel node (SN) in patients with breast cancer is done by tracking a radioactive tracer, a vital dye, or both, as the marker(s) reach the axilla. Replacing this method with ultrasonographic (US) recognition of the SN could eventually spare patients the need for systemic anesthesia, permit minimally invasive outpatient biopsy of the node, and allow the formulation of a precise therapeutic plan before a definitive surgical procedure.

Methods

Eighty-eight axillae of 84 patients with a histologic diagnosis of breast cancer were studied by injecting the subareolar area of the affected breast(s) with technetium 99 and an iron preparation before the planned surgical procedure and SN biopsy. An axillary US scan was performed in all patients before the injection of the markers. After induction of anesthesia, the SN was identified, needle-localized, and extracted under US guidance. Confirmation that the SN was retrieved was established by concordance with the audible gamma signal, unless there was none. All extracted nodes had iron stains performed.

Results

All except three of the SNs were identified with US after the iron marker was injected, and all except six were identified by their radioactive signal. One of the SNs undetected on US was identified by its radioactive tracer, and the other two, although seen on US, had neither a gamma signal nor concordant iron deposits. All other SNs identified with US had a concordant audible signal when there was one, and all had concordant iron deposits on microscopy. Of the six SNs without a gamma signal, three without preincision activity were identified with US; three with neither a preincision nor an ex vivo signal were seen with US, but two of these were the SNs without a concordant iron deposit.

Conclusions

Using an iron preparation, the SN in patients with breast cancer can be identified with US with an accuracy equal to and perhaps better than that achieved with a radioactive tracer. These findings may change the current diagnostic model and affect the therapeutic algorithm of breast cancer patients.