Sentinel lymph node biopsy in breast cancer: guidelines and pitfalls of lymphoscintigraphy and gamma probe detection

Sentinel node (SN) biopsy appears to offer an alternative to routine axillary lymph node dissection (ALND) for staging patients with breast cancer. Various techniques have been studied for identifying the SN, using vital blue dye or radioactive colloid, and initial reports are promising. The inherent limitations and pitfalls must be clearly understood before SN biopsy can be implemented in dinical practice.

In a prospective trial, the feasibility of using lymphoscintigraphy and gamma probe detection for performing SN biopsy was studied. In 130 consecutive patients with T1-T2, N0 breast cancer, preoperative lymphoscintigraphy was performed with technetium 99m-colloidal albumin. During ALND, the radioactive axillary SNs were localized by the gamma probe. Histopathologic examination of the harvested SNs was compared with the status of the axillary lymph nodes.

Axillary focal accumulations were clearly identified on lymphoscintigraphy in 116 patients (89%). The failure rate was significantly higher in patients who had a previous excision biopsy (36%) than in those with a palpable tumor in situ (4%). Using the gamma probe, radiolabeled axillary SNs were successfully biopsied in 122 patients (94%). Because 18 of these patients did not undergo formal lymphadenectomy, the predictive accuracy of SN biopsy was analyzed in 104 patients. Radioactive nodes revealed metastases in 44 of 104 patients (42%); in 26 of them (59%), these were the only involved axillary nodes. The SN was negative in 60 patients (58%); in one patient the ALND was found to contain metastatic disease (1.7% false negatives). Biopsy of the SN was 98% accurate in predicting the absence of nodal metastases.

There are certain guidelines for performing SN biopsy by lymphoscintigraphy and gamma probe detection. Success depends primarily on an adequate functional capacity of the SN, necessary for sufficient nodal uptake to ensure accurate identification. Lymphoscintigraphy defines the pattern of lymph flow and may prevent failure or false-negative biopsies. Biopsy of the SN is a highly accurate, minimally invasive method of staging patients with breast cancer and can substantially reduce the morbidity and costs of surgical treatment by avoiding unnecessary ALND in the majority of patients.