Determination of sentinel lymph node (SLN) status in primary breast cancer by prospective use of immunohistochemistry increases the rate of micrometastases and isolated tumour cells: Analysis of 174 patients after SLN biopsy

Aim The objective of the present study was to evaluate the prospective use of immunohistochemistry (IHC) for histopathological diagnosis of sentinel lymph node(s) (SLN) in primary breast cancer using stage migration and non-SLN metastases as endpoints in relation to metastatic involvement. Method Serial sectioning and prospective use of IHC were applied to SLN examination in addition to routine haematoxylin–eosin staining in 174 consecutive patients with unifocal T1-T2 breast cancer included in a National Sentinel Node Study. Axillary lymph node dissection (ALND) was performed in all cases with macrometastases, micrometastases and isolated tumour cells (ITC). Results The SLN was found in 173/174 patients and a metastatic foci was found in 50 patients including 28/50 with macrometastases, 16/50 with micrometastases and 6/50 with ITC. IHC detected 3/16 of the micrometastases and 4/6 of ITC. Stage migration from N0 to N1mi was encountered in 3/132 patients by use of IHC. Non-SLN metastases were noted in 15/28 of patients with macrometastases and in 3/16 of patients with micrometastases, whereas no patient with ITC had additional metastases (p = 0.007). Conclusion The prospective use of IHC and serial sectioning for histopathological diagnosis of SLNs increased the detection rate of N1mi and ITC, but only 3/132 patients were stage-migrated by use of IHC. Patients with ITC did not have any risk of non-SLN metastases, supporting that ALND can safely be omitted in this group of patients.