Sentinel lymph node micrometastasis as a predictor of axillary tumor burden.

The sentinel lymph node biopsy (SLNB) procedure is an alternative method for assessing the axillary lymph node (ALN) status in patients with breast cancer. The SLNB carries the risk of a false-negative result, with patients harboring positive ALNs in the face of a negative SLNB examination. In addition, the significance of a SLNB with cells identified only with keratin or with deposits less than 0.2 mm remains unresolved. We analyzed our SLNB data over the past 5 years in order to determine the relationship between SLN tumor burden and ALN tumor burden. Pathology files for the past 5 years at Magee-Womens Hospital were searched for all SLNB cases that had an axillary lymph node dissection (ALND). Each SLNB case was reviewed and tabulated for breast tumor size, SLN tumor size, and largest tumor size in the ALND. Correlation and frequency distribution were performed for the status of all SLNs and ALNDs. Patterns of lymph node metastasis were recorded and the sizes of the SLN metastases were reported according to the recent Philadelphia Consensus Conference on Sentinel Lymph Nodes and the revised American Joint Committee on Cancer (AJCC) staging. SLN metastases were classified as immunohistochemistry (IHC) positive if only single keratin-positive cells or clusters were present and were not observed with standard tissue stains, as submicrometastatic (SMM) if tumors were less than 0.2 mm (excluding IHC positive), as micrometastatic if tumors were larger than 0.2 mm but