Ki-67 and ProExC are useful immunohistochemical markers in esophageal squamous intraepithelial neoplasia

Esophageal squamous intraepithelial neoplasia has been widely recognized as a precursor lesion for esophageal squamous cell carcinoma. Early detection offers the best prognosis for esophageal squamous cell carcinoma. The differentiation of squamous dysplasia from reactive change and the classification of squamous dysplasia into high-grade or low-grade are sometimes subjective and challenging. In this study, we sought to evaluate multiple biomarkers and to develop clinically useful adjunct tools for difficult esophageal squamous intraepithelial neoplasia cases. Immunohistochemical stains using antibodies against Ki-67, ProExC, p16, and p53 were performed on esophageal biopsy or resection specimens from 25 patients including 35 foci of high-grade dysplasia and 25 foci of low-grade dysplasia, and from 10 control cases containing 52 foci of normal/reactive hyperplasia. In situ hybridization tests for human papillomavirus were performed in 11 cases. The immunostains for all 4 markers were scored as negative, intermediate, and strong according to established criteria. Intermediate and strong Ki-67 and ProExC staining showed similar detecting power and exhibited very high sensitivity and specificity for distinguishing normal/reactive hyperplasia from esophageal squamous intraepithelial neoplasia and normal/reactive hyperplasia from low-grade esophageal squamous intraepithelial neoplasia. Strong Ki-67 staining was exclusively seen in high-grade esophageal squamous intraepithelial neoplasia, which provided additional value in distinguishing high-grade from low-grade esophageal squamous intraepithelial neoplasia. Strong ProExC staining was also seen in most high-grade esophageal squamous intraepithelial neoplasia foci (80%). Although the frequencies of intermediate/strong staining patterns of p53 increased with increasing degree of dysplasia, the sensitivity of p53 was much lower than that of Ki-67 and ProExC. p16 did not show consistent immunostain pattern in the normal/reactive hyperplasia and esophageal squamous intraepithelial neoplasia. Two (18%) of 11 tested cases were positive for human papillomavirus infection. This study demonstrates that both Ki-67 and ProExC can be used as an adjunct tool for diagnosing difficult cases of esophageal squamous intraepithelial neoplasia.