Scoring mechanisms of p16INK4a immunohistochemistry based on either independent nucleic stain or mixed cytoplasmic with nucleic expression can significantly signal to distinguish between endocervical and endometrial adenocarcinomas in a tissue microarray study

Abstract

Background: Endocervical adenocarcinomas (ECAs) and endometrial adenocarcinomas (EMAs) 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 3 different scoring mechanisms of p16INK4a immunohistochemical (IHC) staining in distinguishing between primary ECAs and EMAs.

Methods: A tissue microarray (TMA) was constructed using formalin-fixed, paraffin-embedded tissue from hysterectomy specimens, including 14 ECAs and 24 EMAs. Tissue array sections were immunostained with a commercially available antibody of p16INK4a. Avidin-biotin complex (ABC) method was used for antigens visualization. The staining intensity and area extent of the IHC reactions was evaluated using the semi-quantitative scoring system. The 3 scoring methods were defined on the bases of the following: (1) independent cytoplasmic staining alone (Method C), (2) independent nucleic staining alone (Method N), and (3) mean of the sum of cytoplasmic score plus nucleic score (Method Mean of C plus N).

Results: Of the 3 scoring mechanisms for p16INK4a expression, Method N and Method Mean of C plus N showed significant (p-values < 0.05), but Method C showed non-significant (p = 0.245) frequency differences between ECAs and EMAs. In addition, Method Mean of C plus N had the highest overall accuracy rate (81.6%) for diagnostic distinction among these 3 scoring methods.

Conclusion: According to the data characteristics and test effectiveness in this study, Method N and Method Mean of C plus N can significantly signal to distinguish between ECAs and EMAs; while Method C cannot do. Method Mean of C plus N is the most promising and favorable means among the three scoring mechanisms.

Figure 1

Immunohistochemical analysis of p16^INK4a staining in endocervical adenocarcinomas. (a) Photomicrograph revealed adenocarcinoma of endocervix, endocervical type, H&E stain. (b) Photomicrograph revealed tumor with more predominant p16^INK4a staining at nuclei than that at cytoplasms. Focally moderately positive nucleic staining and no cytoplasmic staining were identified. (c) Photomicrograph revealed tumor with more predominant p16^INK4a staining at cytoplasms than that at nuclei. Diffusely moderately positive cytoplasmic staining and focally weakly nucleic staining were identified. (d) Photomicrograph revealed tumor with dual prdominat p16^INK4a staining at both cytoplasms and nuclei. Diffusely strongly positive nucleic staining and cytoplasmic staining were identified. All photomicrographs a, b, c, d were taken in median-powered, ×200

Figure 2

Immunohistochemical analysis of p16^INK4a staining in endometrial adenocarcinomas. (a) Photomicrograph revealed adenocarcinoma of endometrium, endometroid type, H&E stain. (b) Photomicrograph revealed tumor with more predominant p16^INK4a staining at nuclei than that at cytoplasms. Diffusely moderately positive nucleic staining and no cytoplasmic staining were identified. (c) Photomicrograph revealed tumor with more predominant p16^INK4a staining at cytoplasms than that at nuclei. Diffusely moderately positive cytoplasmic staining and focally weakly nucleic staining were identified. (d) Photomicrograph revealed tumor with dual prdominat p16^INK4a staining at both cytoplasms and nuclei. Diffusely strongly positive cytoplasmic staining and nucleic staining were identified. All photomicrographs a, b, c, d were taken in median-powered, ×200.

Figure 3

Scatter plots showing the Spearman's rho correlation coefficients (p value) for the associations between pairs of these three types of p16^INK4a scoring mechanisms in endocervical adenocarcinomas and endometrial adenocarcinomas. (1) a1/a2 and d1/d2: Method C was positively correlated with Method N in EMAs, but was not in ECAs. (2) b1/b2 and e1/e2: Method C was positively correlated with Method Mean of C plus N in EMAs but was not in ECAs. (3) c1/c2 and f1/f2: Method N was positively correlated with Method Mean of C plus N in both EMAs and in ECAs.