Detection of micrometastasis in the sentinel lymph nodes in breast cancer

The axillary lymph node (ALN) status is still the most important prognostic factor in the staging and treatment of breast cancer. Intraoperative lymphatic mapping and sentinel lymphadenectomy techniques were investigated in patients with early-stage breast cancer who did not have clinically palpable ALNs.

Forty-four patients with breast cancer underwent a sentinel lymph node biopsy (SLNB), followed by a complete axillary lymphadenectomy. Sentinel lymph nodes (SLNs) were detected by means of so-called 2-way mapping with coloring matter and an isotope. Our standard protocol for evaluating metastasis in SLNs included a frozen section at 1 level for reverse transcription polymerase chain reaction (RT-PCR), plus a paraffin section at 1 level for immunohistochemistry (IHC) of cytokeratin 19, while the rest were evaluated by hematoxylin-eosin (H&E) staining.

SLNs were identified in 42 (95%) of 44 patients. Twenty-one patients had no metastasis in SLNs; however, ALN metastasis was found in 3 patients. Of these 3 patients, 2 had micrometastasis detected by means of either IHC or RT-PCR. Therefore the false-negative rate was decreased from 7% (3/44) to 2% (1/44). Furthermore, of the remaining 18 ALN-negative patients, micrometastasis was detected by means of either IHC or RT-PCR in 7 (39%) patients.

We suggest that SLNB is recommended to detect micrometastasis by means of H&E staining, IHC, and RT-PCR. Omitting ALN dissection referred by SLNB should be avoided if SLNs were evaluated only by H&E staining, and/or IHC without RT-PCR.