Re-evaluation of axillary skip metastases in the era of sentinel lymph node biopsy in breast cancer.

PURPOSE: To investigate whether skip axillary metastases are really skip metastases or a continuation of level I micrometastases in invasive breast cancer, and to determine whether there are any factors predisposing to skip metastases.
METHODS: We reviewed 568 consecutive patients with breast cancer who underwent complete axillary lymph node dissections (ALND) between January 1998 and December 2004. For patients with skip axillary lymph node metastases, resectioning and immunohistochemical staining of the remaining part of paraffin blocks from level I lymph nodes were done to determine whether there were any micrometastases in this group of lymph nodes.
RESULTS: Skip axillary metastases were found in 27 (10%) of 268 patients with axillary lymph node metastases. Re-evaluation of the level I lymph nodes, both with thin sectioning and immunohistochemical staining, in the patients with axillary skip metastases revealed no micrometastases. No significant correlation was found between the demographic and histopathological variables of the patients with skip metastases and those with regular axillary metastases.
CONCLUSIONS: These results suggest that skip axillary metastases are actual skip metastases, not a continuation of undetected level I micrometastases. Moreover, none of the clinical and histopathological measures of primary tumors are predictors of the presence of skip metastases.