Implementation of step sectioning in the examination of sentinel lymph nodes to improve the detection of micrometastases in breast cancer patients

The object of this study was to examine whether a new protocol for examination of sentinel lymph nodes (SLNs) would lead to the detection of more metastases. Sections of 1 mm would identify most SLN macrometastases, and step sections at intervals of 200-250 μm would identify most micrometastases. A total of 111 breast cancer patients who underwent the SLN procedure at St. Olavs University Hospital in Trondheim, Norway in 2008 were included in the study group. Their SLNs were processed according to a new standardized protocol with sections of 2-3 mm being step sectioned at intervals of 200-250 μm. A total of 109 breast cancer patients undergoing the SLN procedure in 2007 were used as a reference group. Metastases were found in 29% of the cases, compared with 26% in the reference group. Step sectioning of SLNs revealed metastases in five cases initially found to be negative. The metastases of the study group were smaller, with a median value of 1.25 mm compared with 4.25 mm in the reference group. Step sectioning led to the detection of metastases in SLNs initially found to be negative. The median size of the metastases was considerably smaller in the study group than in the reference group.