The incidence rates of cervical adenocarcinoma have been increasing over the last two decades, contrary to those of squamous cell carcinoma. This trend is particularly evident among females aged <40 years and has occurred despite extensive cytology-based screening programs. The aim of the present retrospective database study was to investigate adenocarcinoma in situ (AIS) with respect to previous cytological results, high-risk (HR) human papillomavirus (HPV) infections and histological results from AIS-adjacent squamous mucosa. Databases were used to identify 32 female patients with AIS treated for various conditions between 2009 and 2012 at the Department of Gynecology, Uppsala University Hospital (Uppsala, Sweden) and previous cytological, HPV and histological results. Of the individuals in the study, 64.3% had a previously recorded cytological result showing squamous cell abnormalities; five had glandular cell abnormalities (18%) and two had AIS (7.1%). Among the patients with available HPV results, 95% were HR-HPV-positive; HPV18/45 predominated (77%), followed by HPV16 (27%). The patients with multiple HPV infections were aged <= 32 years, while patients aged >= 38 years were only infected with HPV18/45. All but three patients had cervical intraepithelial neoplasia (CIN) in the AIS-adjacent squamous mucosa, 79% of which was CIN2 or worse. The present retrospective database study suggests that AIS is detected at screening mainly due to simultaneous squamous precursor lesions and that HPV18/45 infection is an increasing co-factor for AIS in older patients. HPV analyses of glandular precursor lesions aid in the identification of female individuals at risk of progression to invasive disease, and thus have a favorable effect on adenocarcinoma prevention, together with vaccination.