Adenocarcinoma in situ and adenocarcinoma of the cervix

Definition

• Cervical adenocarcinoma in situ (AIS) is a pre-invasive lesion of the endocervical glandular epithelium and, because of its morphology, is regarded as the precursor of invasive adenocarcinoma.
• Most invasive adenocarcinomas develop from AIS located within or just proximal to the transformation zone.

Classification

Why this special case matters

• Adenocarcinoma arises from the columnar epithelium of the endocervix.
• Cytology therefore detects it less well — it sits endocervically, outside the classic sampling zone.
• The cytology report then carries the suffix g (glandular), e.g. Pap IIIg or IVa-g.

Adenocarcinoma in situ (AIS)

• What sets it apart from CIN: AIS is more often multifocal and discontinuous ("skip lesions").
• Adenocarcinoma is HPV-associated in the majority, especially HPV 18 and 16.

Occurrence & epidemiology

Epidemiology

• About 80–85 % of cervical cancers are squamous cell carcinomas and most of the rest are adenocarcinomas; the proportion of adenocarcinoma has increased over the past two decades.
• Patients with AIS are on average about 5 years younger than those with early invasive adenocarcinoma, reflecting a window of about 5 years between the two.

Aetiopathogenesis

Aetiology and risk factors

• HPV infection is the cause of most cervical cancers; AIS harbours HPV types similar to those found in invasive adenocarcinoma.
• A coexisting squamous neoplasia is common, found in about 55 % of women with AIS in a meta-analysis of 33 studies, reflecting a shared aetiology.

Clinical features

• AIS is almost always asymptomatic and generally not visible on gross examination.
• The lesions lie within the endocervical canal and the glandular clefts and are often multifocal.

Diagnosis

• AIS is usually detected during work-up of an abnormal cervical smear, often actually because of accompanying squamous cell abnormalities.
• Cytology detects glandular lesions poorly, with a sensitivity of only about 45 % in a cited study; adding an HPV test improves detection.
• The colposcopic appearance of AIS is non-specific, and because of their location in the endocervical canal the lesions are difficult to detect colposcopically.

Keep learning in the app

Further reading (selection)

1. Cervical Screening Results Leading to Detection of Adenocarcinoma in Situ of the Uterine Cervix (Asian Pac J Cancer Prev 2019, PubMed Central)
2. MSD Manual Professional: Cervical Cancer
3. DocCheck Flexikon, Adenokarzinom

Cross-references