Objectives: To evaluate the significance of p16(INK4A) protein expression and positivity for HPV DNA in distinguishing between endocervical and endometrial adenocarcinoma.
Methods: Expression of p16(INK4A) protein in 30 cases of endocervical adenocarcinoma and 10 cases of endometrial adenocarcinoma was assessed by immunohistochemistry. In-situ hybridization for human papillomavirus (HPV) DNA was also performed in 20 cases of endocervical adenocarcinoma and 10 cases of endometrial adenocarcinoma.
Results: The positive rate for p16(INK4A) in endocervical adenocarcinoma was 70% (21/30), as compared with 30% (3/10) in endometrial adenocarcinoma. The tumor cells in endocervical adenocarcinoma showed diffuse and strong expression of p16(INK4A) protein with both cytoplasmic and nuclear staining. In contrast, the endometrial adenocarcinoma cells showed patchy and weak expression of p16(INK4A). On the other hand, HPV DNA (type 16 or 18) was detected by in-situ hybridization in 9 (45%) of the 20 cases of endocervical adenocarcinoma and none of the 10 cases of endometrial adenocarcinoma.
Conclusions: The expression of p16(INK4A) protein is significantly higher in endocervical adenocarcinoma than in endometrial adenocarcinoma. This expression pattern can serve as a useful immunohistochemical marker in the differential diagnosis. p16(INK4A) protein immunohistochemistry appears to be more sensitive than HPV DNA testing in distinguishing between endocervical and endometrial adenocarcinoma, especially in biopsy or curettage specimens.