This chapter describes abnormality of glandular cells. Atypical glandular cell (AGC) abnormality is classified by the Bethesda system (TBS) 2001/TBS 2014 as atypical endocervical in origin, atypical endometrial in origin, endocervical adenocarcinoma in situ, and adenocarcinoma. TBS 2001/2014 encouraged to determine the origin of the atypical glandular cell (AGC) such as endocervical or endometrial. The terminology “Atypical glandular cell of undetermined significance” has been eliminated in TBS 2001/2014. Endocervical adenocarcinoma in situ has been kept as an individual entity in TBS 2001/2014. Atypical endocervical cells show cytological atypia exceeding that of reactive endocervical cells but fall short the cytological features of adenocarcinoma in situ or adenocarcinoma. Atypical endometrial cells show multiple small cohesive clusters of endometrial cells. The cytoplasm of the cell is scanty. Adenocarcinoma in situ (AIS) lesions of cervix is the precursor lesion of adenocarcinoma and is much less common than cervical intraepithelial neoplasia.