Comparison of immunohistology using pan-CK and EMA in the diagnosis of lymph node metastasis of gastric cancer, particularly micrometastasis and isolated tumor cells.

The aim of this study was to identify a suitable method for detecting lymph node metastasis of gastric cancer (GCA) by hematoxylin and eosin (HE) and immunohistochemical (IHC) staining. We investigated lymph node metastasis using pan-cytokeratin (CK) and epithelial membrane antigen (EMA) IHC staining in a total of 1,422 lymph nodes from 100 patients who underwent radical gastrectomy between 2007 and 2009. Of 700 intestinal and 722 diffuse type GCA lymph nodes, the metastasis rates were significantly different when using conventional HE staining only or HE supplemented with IHC (P<0.01). The metastasis rate of the intestinal type was 31.71% using HE staining, 35.71% with HE and pan-CK, 35.57% with HE and EMA and 35.71% with combination examinations of all three. The false-positive rate was zero with pan-CK, 12.67% with EMA and 18.57% with all three. The metastasis rate of the diffuse type was 27.70% using HE staining, 36.01% with HE and pan-CK, 35.04% with HE and EMA and 36.01% with all three. The false-positive rate was zero with pan-CK, 7.58% with EMA and 11.86% with all three. For both types, the true-positive and -negative rates of pan-CK were higher than those of EMA. IHC staining is unnecessary if lymph node metastasis is detected in HE staining. If HE staining does not reveal metastasis, pan-CK staining should be performed for further diagnosis.