Histopathologic analysis of sentinel lymph nodes in breast carcinoma.

Background: Intraoperative lymphatic mapping and identification of the first draining lymph node (the sentinel lymph node) may allow some patients with breast cancer to avoid the morbidity of formal axillary clearance. The aim of this study was to determine the accuracy of sentinel lymph node (SLN) biopsy in predicting axillary nodal involvement.

Methods: From August, 1998 until July, 1999, 41 patients with clinically node-negative breast cancer underwent SLN biopsy that was immediately followed by axillary lymph node dissection. If the SLN section was found free of metastasis by routine hematoxylin and eosin staining (H&E), then an additional four sections of the SLN were cut and examined for the presence of tumor cells by H&E staining (three sections) and by cytokeratin immunohistochemical staining (IHC) (one section). If the SLN had metastatic cells and the other remaining nonsentinel axillary lymph nodes were free of metastases by routine H&E staining, then an additional three sections of the nonsentinel axillary lymph nodes were cut and examined for the presence of tumor cells by H&E staining.

Results: The 41 patients had a mean of 2.2 sentinel (range, 1-7) and 14.6 nonsentinel (range, 5-32) lymph nodes excised per patient. Routine H&E staining identified 13 patients (31.7%) with SLN metastases and 28 patients (68.3%) with tumor-free SLNs. Applying IHC and the additional three sections stained with H&E to these tumor-free SLNs showed one additional patient with sentinel node metastasis. The conversion rate from being a sentinel node-negative patient to a sentinel node-positive patient was 3.6% (1/28). Overall, SLN metastases were detected in 14 (34.1%) of the 41 patients. The SLNs were negative in 27 patients (65.9%), two of whom had at least one positive nonsentinel lymph node each (7.4% "skip" metastasis). Biopsy of SLNs was 92.6% accurate in predicting the absence of nonsentinel nodal metastasis (p=0.001).

Conclusions: Our results suggest that formal axillary lymph node dissection may need only be performed in SLN-positive patients. Nonetheless, further experience and refinement are needed to perfect this technique.