Studies suggest that immunohistochemistry improves rate of detecting sentinel lymph node
metastases and is needed for adequate staging in invasive
lobular carcinoma. Our study evaluates the use of
cytokeratin immunohistochemistry in detecting sentinel lymph node
metastases and its effect on staging patients with invasive
lobular carcinoma. Material from 76 patients with invasive
lobular carcinoma was reviewed.
Cytokeratin immunostaining was performed on negative nodes, and deposits were classified as macrometastasis (>2.0 mm),
micrometastasis (>0.2-2 mm), or isolated
tumor cells (<or=0.2 mm). Of 76 cases, 24 (21 macro- and 3
micrometastases, 32%) were positive for
metastasis and 14 (18%) for isolated
tumor cells. Immunohistochemistry was needed for all cases with isolated
tumor cells and 1 case of
micrometastasis. Criteria to distinguish isolated
tumor cells and
micrometastasis need to be better defined. In our study, immunostaining changed nodal status and stage in 1 of 52 (2%) node-negative patients. Immunohistochemistry is essential to detect isolated
tumor cells in sentinel lymph nodes. However, for detecting micro- or macrometastases, it does not provide any significant advantage over detailed histopathological evaluation of sentinel lymph node.