The accurate distinction between primary endocervical adenocarcinomas (ECA) and endometrial adenocarcinomas (EMA) may require the use of multiple ancillary monoclonal antibodies in panels of immunohistochemistry stains. In addition to reappraising the expressions of four commonly used individual monoclonal antibodies [estrogen receptor (ER), Vimentin (Vim), carcinoembryonic antigen (CEA), and p16(INK4)], this study was designed to investigate whether CEA and p16(INK4) can be effectively exchanged between two relevant three-marker panels (ER/Vim/CEA vs. ER/Vim/p16(INK4)) in distinguishing ECA from EMA. A tissue microarray was constructed using paraffin-embedded, formalin-fixed tissues from 35 hysterectomy specimens, including 14 ECA and 21 EMA. Utilizing the avidin-biotin technique, tissue array sections were immunostained with the four aforementioned individual markers (ER, Vim, CEA, and p16(INK4)). In addition to the four individual monoclonal antibodies, both their respective three-marker panels, proposed here, showed statistically significant (p < 0.05) frequency differences between these two gynecologic tumors (ECA vs. EMA). The panel performance and test effectiveness revealed that both three-marker panels are promising and very helpful. According to our data, when histomorphological and clinical doubt exists as to the primary site of origin, we recommend using either of these two conventional three-marker panels, which consist of ER/Vim/CEA and ER/Vim/p16(INK4). CEA and p16(INK4) can be interchanged with confidence without significantly influencing the panel presentations and efficiencies in distinguishing between adenocarcinomas of endocervical and endometrial origin.