Immunohistochemical Detection of Occult Serosal Micro- invasion in Primary Lesions of Gastric Cancer with Sub- serosal Invasion

In gastric cancer, the presence or absence of serosal invasion by cancer in the primary lesion is an important prognostic factor. Pathological findings are routinely determined by hematoxylin-eosin (H&E) staining, but it is well known that micrometastasis or microinvasion are easily overlooked by H&E staining. Cytokeratin (CK) proteins serve as reliable markers for cells from epithelial origins. The purpose of this study was to clarify the usefulness of CK immunohistochemical staining in the detection of serosal microinvasion in gastric cancer with subserosal invasion. We examined 50 primary lesions from 50 gastric cancer patients with subserosal invasion. Two consecutive sections were prepared for simultaneous staining with ordinary H&E and CK immunostaining with anticytokeratin antibody (CAM 5.2), respectively. Although there were no differences in the postoperative survival rates between patients with or without microinvasion, serosal microinvasion was 0detected in 8 (16%) of 50 patients by CK staining, including 1 patient whose invasion was detected by both H&E and CK stainings. CK immunostaining enabled us to make an accurate and detailed diagnosis which we believe to be useful for detecting serosal microinvasion in the primary lesion in gastric cancer with subserosal invasion.