Pathologic examination of sentinel lymph nodes in breast cancer by a single haematoxylin-eosin slide versus serial sectioning and immunocytokeratin staining: clinical implications

Background The objective was to determine the additional value of pathologic examination using three-level sectioning and immunocytokeratin (ICK) staining of sentinel lymph node (SN) biopsies in cT1-2N0M0 breast carcinoma patients regarding lymph node staging and eligibility of systemic therapy taking primary tumor characteristics in account. Methods SN slides of 277 patients out of a total group of 961 patients known to have tumor-positive SNs detected by three-level sectioning and ICK staining were re-examined. Haematoxylin-eosin (HE) slide level three was scanned for tumor deposits, and when present, extra capsular extension, maximum tumor diameter and number of positive SNs was noted. In addition, slides of the axillary dissection of non-SNs were reviewed, with determination of metastasis size and number of positive non-SNs. Primary tumor characteristics (grade, diameter, estrogen receptor) were recorded. Results In the single-HE examination, 26 cases SN micrometastasis and 6 macrometastasis were missed, 3 cases of micrometastasis were incorrectly classified as isolated tumor cells, and 9 patients with macrometastasis were misclassified as micrometastasis. In addition, in the tumor-negative single-HE examination, additional axillary lymph node dissection (ALND) revealed 6 cases of non-SN metastasis. Taking primary tumor factors into account for adjuvant systemic therapy, 21 patients would have been denied the choice for systemic therapy if single-HE examination was carried out only. Conclusions Single-HE examination of SN may result in a reduction of locoregional and systemic treatment according to treatment guidelines then current in the Netherlands.