Size of sentinel node tumor deposits and extent of axillary lymph node involvement: Which breast cancer patients may benefit from less aggressive axillary dissections?

Background: In most breast cancer series, nearly 30% to 40% of all patients are sentinel node positive; however, in a large proportion of these, the disease is limited to three or fewer positive nodes. On the basis of these observations, the object of this study is to identify a subset of patients who might benefit from a less aggressive axillary dissection, without compromising staging or local disease control. We reviewed known clinicopathologic variables associated with a higher risk for axillary metastasis in 467 patients who underwent sentinel node mapping at our institution. We then compared the incidence of these variables in patients with N1a versus N2-3 stage disease. Results: Although the presence of lymphvascular invasion in the primary tumor and extracapsular extension of tumor in the sentinel node were statistically significantly different between N1a and N2-3 patients (P < .025 and P < .01, respectively), the variable that most reliably separated N1a from N2-3 patients was the size of the tumor deposits in the sentinel node (P < .001). All patients with sentinel node tumor deposits ≤5 mm had three or fewer positive nodes; 95% were sentinel node-positive only, and 91% had single-node involvement. Conclusions: Patients at low risk for extensive axillary nonsentinel node involvement may benefit from a more conservative surgical approach to their axillae, perhaps limited to sentinel node biopsy only or to axillary procedures restricted to the group of axillary nodes in close proximity to those designated as sentinel nodes.