Aims: Sentinel lymph node biopsy has replaced the axillary lymph node dissection (ALND) in primary surgery for breast cancer in many hospitals and is expected to become the standard of care in due time. Since the sentinel lymph node is subjected to more extensive pathologic examination than the lymph nodes in the axillary dissection specimen, more patients are found to be node positive (N+); however many of them contain micro-metastases (<or=2mm). The consequence may be an overshoot of therapy: additional surgery for non-metastatic lymph nodes or systemic adjuvant therapy.
Methods: We examined 34 (out of a series of 38) clinically T1 (cT1) patients who had a SLN biopsy with or without ALND and compared them to a matched historical control group.
Results: Twenty-one of 34 (62%) patients showed tumour cells in their SLN's. From these 21 patients in 13 (62%) the SLNs contained isolated tumour cells, of which 10 (77%) were detected only by immunohistochemistry (IHC), in four (19%) the SLNs contained micrometastases, and in four (19%) macrometastases. From 16 patients with isolated tumour cells or micrometastases in the SLN who underwent a regular ALND one had an H&E detected isolated tumour cell in a non-SLN and one patient with isolated tumour cells in the SLN who did not get a regular ALND developed an axillary recurrence 11 months after the primary treatment. On the other hand, three of four (75%) patients with macrometastases in the SLN had pathologically involved non-SLNs. In the majority (70%) of patients of the historical control group no lymph node involvement was seen. The percentage of macrometastases staged as lymph node positive in the control group was the same as in the studied group.
Conclusion: Most patients with cT1 breast cancer with isolated tumour cells or micrometastases in the SLN will not benefit from additional axillary dissection; 88% had a negative ALND. Since we cannot select the group that will benefit from ALND, this is still indicated in case of isolated tumour cells or micrometastases in the SLN. Since most of the affected SLNs show isolated tumour cells and are classified as pN0(i+), stage migration due to more meticulous pathologic examination does not occur according to the TNM classification. However some patients do not benefit from the introduction of the SLN, due to the high incidence of isolated tumour cells or micrometastases in the SLN. Many more patients than expected still end up with an ALND.