Neoplastic changes of the cervical epithelium Ė Adenocarcinoma in situ (AIS)
Precancerous lesions arising from the columnar epithelium are referred to as adenocarcinoma in situ (AIS). The cause of AIS is also persistent infection with high-risk HPV types, of which types 16 and 18 are most common. AIS is much more difficult to detect compared with CIN, because the lesion is invariably within the endocervical canal. AIS is also difficult to treat. The lesions are not only hidden inside the canal but also can be multifocal (skip lesions). If left untreated, AIS may give rise to adenocarcinoma in 5Ė10 years. AIS and CIN often coexist.
The next section provides more information about invasive cervical cancers.