Immunohistochemical detection of occult metastases in paraaortic lymph nodes in advanced gastric cancer.

Some Japanese surgeons have examined the utility of super-extended paraaortic lymphadenectomy (PAL) as part of the surgical treatment for advanced gastric cancer. However, therapeutic value of this PAL remains controvertial. The purpose of this study was to evaluate appropriate candidates who might benefit from PAL by the immunostaining with cytokeratin (CK) of the macroscopically intact paraaortic nodes. A total of 525 paraaortic nodes from 35 patients was serially sectioned and stained with hematoxylin-eosin (H&E) and CK staining. A total of 17 nodes (3.2%) from 7 patients (20.0%), among 525 macroscopically intact paraaortic nodes, was determined to be immunopositive for CK. In 4 patients, 8 H&E-positive nodes with metastases were all immunopositive and, in addition, 4 H&E-negative nodes were also immunopositive. Furthermore, 3 patients with H&E-negative nodes had five immunopositive nodes. Immunostaining with CK was useful for detection of occult metastases. Survival was prolonged in 3 of these 7 patients. The incidence of CK-positive nodes was significantly higher in patients with gross type of 3 or 4 gastric cancer and in patients with H&E-detected nodal metastasis within group 3 (N3) nodes. It seems that such patients would benefit from prophylactic PAL.