Your diagnosis

Adenocarcinoma in situ (AIS) of the cervix

This article will help you read and understand your pathology report for adenocarcinoma in situ (AIS) of the cervix.

by Emily Goebel, MD FRCPC, updated March 11, 2021

adenocarcinoma in situ cervix


Quick facts:
The cervix

The cervix is part of the female genital tract. It is found at the bottom of the uterus where it forms an opening and a canal into the endometrial cavity of the uterus.

The outer surface of the cervix is lined by two types of cells that form a barrier called the epithelium. The first part of the cervix is called the exocervix and it is lined by squamous cells. The second part of the cervix is called the endocervical canal and it is lined by rectangular shaped cells which connect together to make small structures called glands. The tissue below the epithelium is called the stroma and is made up of connective tissue and blood vessels.

What is endocervical adenocarcinoma in situ (AIS)?

Endocervical adenocarcinoma in situ (AIS) is a type of non-invasive cervical cancer. The disease starts in the cervix from the glands in the endocervical canal. AIS is called non-invasive because the cancer cells are seen only in the epithelium. If not treated, AIS can turn into a type of invasive cancer called endocervical adenocarcinoma.

What causes endocervical adenocarcinoma in situ?

Most cases of AIS and endocervical adenocarcinoma in the cervix are a result of the normal endocervical cells in the cervix becoming infected with a high-risk type of virus called human papillomavirus (HPV).

How do pathologists make this diagnosis?

The diagnosis of AIS is usually made after a small sample of tissue is removed from the cervix during a Pap test. The diagnosis can also be made after a larger sample of tissue is removed in a biopsy or resection.​

What is p16?

Cells infected with high-risk types of human papillomavirus (HPV) produce large amounts of a protein called p16. Your pathologist may perform a test called immunohistochemistry to look for p16 inside the abnormal cells.

This test will confirm the diagnosis of AIS and rule out other conditions that can look like AIS under the microscope. Almost all cases of AIS are positive or reactive for p16 which means your pathologist saw the p16 protein in the cancer cells.

What to look for in your report after the tumour has been removed


A margin is any tissue that has to be cut by the surgeon in order to remove the tumour from your body. Pap smears do not have margins.


If you underwent a surgical procedure to remove the entire tumour from your body, your pathologist will examine the margin closely to make sure there are no cancer cells at the cut edge of the tissue.

The number and type of margins will depend on the type of procedure performed to remove the tumour from your body. Typical margins include:

  • Endocervical margin – This is where the cervix meets the inside of the uterus.
  • Ectocervical margin – This is the bottom of the cervix, closest to the vagina.
  • Stromal margin – This is the tissue inside the wall of the cervix.

A margin is considered positive when AIS is seen at the edge of the cut tissue.

Finding cancer cells at the margin increases the risk that the tumour will grow back in that location.

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