High incidence of micrometastases in breast cancer sentinel nodes

Background: Sentinel lymph node biopsy (SLNB) is being investigated as an alternative to formal axillary dissection in early breast cancer. Avoiding the morbidity of unnecessary axillary dissection is seen as the main potential benefit of SLNB. Sentinel lymph node biopsy also allows enhanced pathological analysis. A series of 62 sentinel node (SN) biopsies demonstrating a high incidence of micrometastases is presented here. Methods: All SN were initially examined and reported by H&E staining. All negative SN were analysed after staining with polyclonal anticytokeratin antibody. Results: Sixty-two patients underwent SLNB at Royal Melbourne Hospital between May 1998 and February 2000. One or more SN was identified in 51/62 patients. A total of 10/51 contained metastases identified after H&E staining. There was one false negative. A total of 10/41 patients with H&E-negative SN had micrometastases identified on immunohistochemistry (IHC). Micrometastases were more common in patients with larger tumours, with disease found in the H&E-negative SN of 1/17 T(1)a and T(1)b (1-10 mm), 4/15 T(1)c (11-20 mm), and 5/9 T-2 (20-50 mm) tumours. Conclusion: Sentinel lymph node biopsy can accurately assess the axilla in most patients with early breast cancer. A significant proportion of histologically negative SN will have micrometastases identifiable with IHC. Although the clinical significance of such metastases is uncertain, the available evidence suggests that these patients have a poorer prognosis than other patients with negative lymph nodes.