Pathological validation of sentinel lymph node metastasis in breast cancer

Abstract

OBJECTIVES: Recent studies have suggested that sentinel lymph nodes (SLN) are the first nodes that receive drainage from breast cancer. Studies also indicate that SLN biopsy is a safe alternative staging procedure for patients with breast cancer. In this sense, it is necessary to carry out lymphatic mapping in order to identify SLNs and prove that they are reliable predictors of axillary lymph node status, based on the pathologic study of SLN and compared with the results of axillary lymph node dissection (LND).
MATERIALS AND METHODS: From April 1999 through August 2000, 50 patients with breast cancer were staged with sentinel lymph node biopsy followed by complete axillary dissection. Three techniques for mapping SLN were used: lymphoscintigraphy with Technetium Tc99m-labeled dextran and, during the transoperative period, detection of radioactivity with gamma probe counter and, simultaneously, blue dye for stained lymphatic ducts or nodes. The study of SLN was carried out using frozen sections and using hematoxilyn and eosin staining (H&E) and cytokeratin immunohistochemical staining (IHC). The LN were studied by standard pathologic H&E.
RESULTS: These patients had a mean age of 56.4 years for a median of 57 years; the mean tumor size was 2.3 cm in diameter for a median 2.0 cm. An average 2.2 (range: 1-5) SLN were excised per patient; and 20.6 was the average of axillary lymph nodes excised. H&E identified 20 patients (40%) with SLN metastasis (SLN+) and 30 patients (60%) with metastasis-free SLN (SLN-). IHC in these 30 patients showed an additional 5 SLN positive patients. Thus, the IHC patient-SLN-conversion was of 17% (5/30). The increased rate of SLN+ was correlated with tumors greater than 2.0 cm. The increased incidence in nonsentinel nodes occurred with primary tumors greater than 2.0 cm and patients aged 50 years or less. The prevalence of SLN+ was of 42% according to H&E. Sensitivity was of 95.2%, negative predictive value of 96.6%, and accuracy of 98%.
CONCLUSIONS: Results indicated that the method is reliable with 2% false-negatives (1/50) when used together with H&E. IHC indicated an upstaging of 17%, most of which were patients with micrometastasis (tumor less than 2 mm). The accuracy of SLN as a predictor of axillary lymph node was 98%. This suggests that axillary lymph node dissection may not be necessary in patients with metastasis free SLN.