Endocervical adenocarcinoma: selected diagnostic challenges. 
Endocervical adenocarcinomas can be classified into two main types of tumors, namely, those related to high-risk human papillomavirus and those unrelated to high-risk human papillomavirus.  The former, representing the vast majority, are referred to as endocervical adenocarcinomas of usual type and the latter are dominated by the gastric-type mucinous adenocarcinomas.  Commonly encountered diagnostic problems concerning these endocervical adenocarcinomas include: (1) diagnosing invasion for endocervical adenocarcinomas of usual type, particularly superficial forms which must be distinguished from extensive endocervical adenocarcinoma in situ; (2) distinguishing high-risk human papillomavirus-related endocervical adenocarcinomas from endometrial endometrioid carcinomas; and (3) distinguishing benign/hyperplastic mucinous endocervical glandular proliferations from gastric-type mucinous endocervical adenocarcinomas, particularly minimal deviation adenocarcinoma.  The current review provides practical points and numerous illustrative examples to guide pathologists in addressing these diagnostic challenges in routine practice.