The biological significance of occult
metastases in axillary lymph nodes of
breast cancer patients is controversial. The purpose of the study was to determine the prognostic significance of occult
micrometastases using the current American Joint Committee on
Cancer (AJCC) staging system in a cohort of women with node-negative
breast cancer, of whom 5% received adjuvant systemic
therapy and who all had long-term follow-up. We studied a cohort of 214 consecutive histologically node-negative
breast cancer patients with a median follow-up of 8 years. Blocks of the axillary lymph nodes were assessed for occult
micrometastases by examination of an additional
hematoxylin-
eosin-stained slide and by immunohistochemical staining using an antibody to low molecular weight
keratin. Occult
metastases were classified according to the sixth edition of the AJCC
cancer staging manual. We examined the prognostic effects of occult
micrometastases and other clinicopathologic features on recurrence outside the breast with disease-free interval (DFI) and survival from
breast cancer with disease-specific survival (DSS).
Cytokeratin-positive
tumor cells were identified in the lymph nodes in 29 of 214 cases (14%). Two cases had isolated
tumor cells and no cluster larger than 0.2 mm [pN0(i+)], whereas 27 of 214 (13%) had
micrometastases (larger than 0.2 mm and <or=2.0 mm] (pN1mi). None of the cases had macrometastases. With median 8 years follow-up, occult
micrometastases were not significantly associated with any of the clinicopathologic features. In addition, occult
micrometastases were not significantly associated with DFI or DSS and thus were not included in the multivariate analysis. On multivariate analysis, lymphovascular invasion was significantly associated with DFI (p < 0.001) and DSS (p = 0.02), whereas percentage S-phase was significantly associated with DSS (p = 0.02). This study, in which 95% of patients did not receive adjuvant systemic
therapy, suggests that
breast cancer patients with occult
micrometastases in axillary lymph nodes have a similar prognosis to those with no
micrometastases. This information is important with regard to the practice of sentinel node biopsy and subsequent axillary node dissection and to the decision to administer adjuvant
therapy based on detection of
micrometastases in lymph nodes.