Immunohistochemical demonstration of cytokeratin is useful for detecting micrometastatic foci from gallbladder carcinoma in regional lymph nodes

Background: The histological detection of lymph node metastasis in patients with gallbladder carcinoma is of major prognostic significance. However, i t may be difficult to identify nodal involvement by conventional pathologic al examination of hematoxylin-eosin (HE)-stained sections when metastases a re of microscopic size. In the present study, an attempt was made to detect lymph node metastasis precisely from gallbladder carcinoma, even by low-po wer microscopic examination, using immunohistochemistry with an anti-cytoke ratin antibody. Methods: A total of 431 lymph node specimens dissected during surgery from 33 patients with carcinoma of the gallbladder were investigated. A pair of mirror-image sections were obtained from each of the dissected lymph nodes and then stained using standard HE and immunohistochemical methods utilizin g a monoclonal antibody against cytokeratin 7. The HE- and immunohistochemi cally stained sections were examined for the presence of tumor cells using light microscopy. Results: All 78 lymph nodes from 12 patients with early gallbladder carcino ma were negative for both HE- and cytokeratin-positive cancer cells. Of 353 lymph nodes from 21 patients with advanced gallbladder carcinoma, HE stain ing showed that 98 were metastasis-positive. Among these 98 lymph nodes, 95 (97%) proved to be positive for metastasis based on cytokeratin immunostai ning. On the other hand, the remaining 255 lymph nodes were cancer-free on the basis of HE staining results. Of the 255 HE-negative lymph nodes, seven (2.7%) were found to be positive for micrometastasis on the basis of cytok eratin staining. Conclusions: Cytokeratin staining of dissected lymph nodes is a useful new diagnostic tool for detecting micrometastatic foci in regional lymph nodes of patients with gallbladder carcinoma.