Immunohistochemistry analysis of micrometastasis in pretreatment lymph nodes from patients with esophageal cancer

Background With recent advances in neoadjuvant therapy in esophageal cancer, pretreatment lymph node staging has become increasingly important in stratifying patients to appropriate treatment regimens and for prognostication. Immunohistochemical analysis (IHC) using epithelial markers has been shown to identify micrometastases in histologically negative lymph nodes. We performed this study to evaluate if IHC analysis in thoracoscopic/laparoscopic (Ts/Ls) pretreatment staging lymph nodes can reveal additional diagnostic information to routine histopathology. Methods Specimens of 106 patients with esophageal cancer who had pretreatment Ts/Ls staging were retrospectively studied. Lymph node biopsies were obtained for IHC staining using cytokeratin (CK) of AE1/AE3. IHC staining for p53, an apoptosis protein associated with poor prognosis in esophageal cancer, was also performed. Results 331 Ts/Ls staging lymph node biopsies were collected from 106 patients. A total of 15.4% (51/331) of the lymph nodes or 34.9% (37/106) of patients were found to have metastatic deposits by routine histology. All the histologically positive lymph nodes were CK positive. Among the remaining 280 histologically negative lymph nodes, 11(3.9%) were found to have micrometastasis by CK staining. Three patients (4.3%, 3/69) were upstaged from N0 to N1. They died of early recurrences after treatment. A total of 67.6% (25/37) of the patients with histologically positive lymph node were p53 positive. No histologically negative lymph node was found to be p53 positive in this series. Conclusions Immunohistochemical analysis for CK can detect micrometastatic involvement of lymph nodes that are missed on routine pathologic examination, and, therefore, can improve lymph node staging. Its clinical significance in esophageal cancer warrants further study.