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, it may be difficult to identify nodal involvement by conventional pathological examination of hematoxylin-eosin (HE)-stained sections when metastases are of microscopic size. In the present study, an attempt was made to detect lymph node metastasis precisely from gallbladder carcinoma, even by low-power microscopic examination, using immunohistochemistry with an anti-cytokeratin 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 utilizing a monoclonal antibody against cytokeratin 7. The HE- and immunohistochemically stained sections were examined for the presence of tumor cells using light microscopy. Results: All 78 lymph nodes from 12 patients with early gallbladder carcinoma were negative for both HE- and cytokeratin-positive cancer cells. Of 353 lymph nodes from 21 patients with advanced gallbladder carcinoma, HE staining showed that 98 were metastasis-positive. Among these 98 lymph nodes, 95 (97%) proved to be positive for metastasis based on cytokeratin immunostaining. 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 cytokeratin 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.