ObjectiveTo determine the likelihood of nonsentinel axillary metastasis in the presence of sentinel node metastasis from a primary breast carcinoma. Summary Background DataSentinel lymphadenectomy is a highly accurate technique for identifying axillary metastasis from a primary breast carcinoma. Our group has shown that nonsentinel axillary lymph nodes are unlikely to contain tumor cells if the axillary sentinel node is tumor-free, but as yet no study has examined the risk of nonsentinel nodaJ invoKlement when the sentinel node contains tumor calls. MethodsBetween 1991 and 1997, axillary lymphadenectomy was performed in 157 women with a tumor-involved sentinel node. Fifty-three axillae (33.5%) had at least one tumor-involved nonsentinel node. The authors analyzed the incidence of nonsentinel node involvement according to clinical and tumor characteristics. ResultsOnly two variables had a significant impact on the likelihood of nonsentinel node metastasis: the size of the sentinel node metastasis and the size of the primary tumor. The rate of nonsentinel node involvement was 7% when the sentinel node had a micrometastasis (.2 mm), compared with 55% when the sentinel node had a macrometastasis (>2 mm). In addition, the rate of nonsentinel node tumor involvement increased with the size of the primary tumor. ConclusionsIf a primary breast tumor is small and if sentinel node involvement is micrometastatic, then tumor cells are unlikely to be found in other axillary lymph nodes. This suggests that axillary lymph node dissection may not be necessary in patients with sentinel node micrometastases from T1/T2 lesions, or in patients with sentinel node metastases from Tl a lesions.Although surgical management of a primary breast cancer has evolved from radical mastectomy to breast-conserving techniques, surgical management of the axilla has changed little. The tumor status of lymph nodes excised during axillary lymph node dissection (ALND) is the best The increased use of screening mammography has resulted in the earlier detection and the smaller size of inva-

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Use of IHC increases the likelihood of detection of NSN metastasis, and the risk of IHC-detected metastasis increases with the size of the SN metastasis and the size of the primary tumor. If SN involvement is micrometastatic (< or =2 mm) or detected by using IHC, tumor cells are unlikely to be found in other axillary lymph nodes in patients with a small primary tumor. The clinical significance of micrometastatic disease in lymph nodes is controversial, and a prospective randomized study is necessary to resolve this important issue.