Scoring of p16(INK4a) immunohistochemistry based on independent nuclear staining alone can sufficiently distinguish between endocervical and endometrial adenocarcinomas in a tissue microarray study.

Endocervical adenocarcinomas and endometrial adenocarcinomas are malignancies that affect uterus; however, their biological behaviors are quite different. This distinction has clinical significance, because the appropriate therapy may depend on the site of tumor origin. The purpose of this study is to evaluate four different scoring methods of p16(INK4a) immunohistochemical staining in distinguishing between primary endocervical adenocarcinomas and endometrial adenocarcinomas from limited sizes of tissue specimens. A tissue microarray was constructed using formalin-fixed, paraffin-embedded tissue from hysterectomy specimens, including 14 endocervical adenocarcinomas and 21 endometrial adenocarcinomas. Tissue array sections were immunostained with a commercially available antibody of p16(INK4a). Avidin-biotin complex method was used for antigens visualization. The staining intensity and area extent of the immunohistochemistry was evaluated using the semiquantitative scoring system. Of the four scoring methods for p16(INK4a) expression, Method Nucleus, Method Dominant Cytoplasm or Nucleus, and Method Mean of Cytoplasm plus Nucleus showed significant (P values <0.05), but Method Cytoplasm did not show significant (P=0.432), frequency distinction between endocervical adenocarcinomas and endometrial adenocarcinomas. In addition, Method Mean of Cytoplasm plus Nucleus had the highest overall accuracy rate (80%) for diagnostic distinction among these four score-counting methods. According to the data in this tissue microarray study, Method Nucleus is the most convenient and efficient method to distinguish between endocervical adenocarcinomas and endometrial adenocarcinomas. Although Method Dominant Cytoplasm or Nucleus as well as Method Mean of Cytoplasm plus Nucleus also revealed statistically significant results, they are relatively more inconvenient due to complicated score calculating means on the basis of mixed cytoplasmic and nuclear p16(INK4a) expressions. Method Cytoplasm is of no use in the diagnostic distinction between endocervical adenocarcinomas and endometrial adenocarcinomas.