Cancer is staged based on how much it has grown and spread to other organs. Sometimes, cancer is caught too early for staging. This is called “in situ,” and it happens when abnormal cells that haven’t yet become cancerous are found.

When those cells are found in the mucus-producing cells of organs, it is known as adenocarcinoma in situ.

Since adenocarcinoma in situ has not yet become cancer, it doesn’t cause any symptoms and is typically very treatable when detected.

Adenocarcinoma is a type of cancer that starts in the glands that produce mucus. Your body has mucus-producing glands in several organs, including:

  • uterus
  • cervix
  • lungs
  • colon
  • pancreas

Adenocarcinoma in situ (AIS) means that there are abnormal cells in these mucus-producing glands, but they aren’t cancerous and have not spread. If left untreated, these abnormal cells could become cancer.

AIS is sometimes referred to as cancer stage 0.

You can develop AIS in any organ that has mucus-producing glands. However, it is most commonly found in the cervix, lungs, pancreas, and colon.

Find out more about the common types of AIS in the sections below.

Cervical

Cervical AIS is the most common type of AIS. It occurs when abnormal cells form in the mucus-producing glands of the cervix.

While cervical AIS will eventually lead to cervical cancer if it’s not treated, the abnormal cells aren’t yet cancerous and haven’t spread.

The condition is often diagnosed in women in their mid- to late-30s.

Lung

Lung AIS occurs when a tumor that is smaller than 3 centimeters (cm) forms in the mucus-producing gland of your lungs. The tumor cells are noncancerous and haven’t grown and spread.

Over time, if the tumor isn’t removed, it could become lung cancer.

Pancreatic

Pancreatic AIS occurs when small tumors develop in your pancreas’s mucus-producing glands. The tumor is confined to the gland and is made of abnormal cells that aren’t yet cancer cells.

Just like with lung AIS, this small tumor could become pancreatic cancer if it is not removed.

Colon

Colon AIS is often referred to as stage 0 colorectal adenocarcinoma. It occurs when a small, noncancerous tumor grows in the mucus-producing gland of your colon. If the tumor isn’t treated, it can spread and become colon cancer.

Most people who have any type of AIS have no symptoms. AIS is often found during screenings or unrelated imaging tests. For example, cervical AIS might be found during a routine pap smear and cervical cancer screening.

When AIS is found, a doctor will likely order a biopsy. During the biopsy, a medical professional will remove a small piece of tissue from the affected organ. They will study the sample to see if the abnormal cells are AIS or another stage of cancer.

You’ll be diagnosed with AIS if the doctor finds that the cells aren’t cancerous and aren’t growing.

The risk factors for AIS are the same as the general risk factors for cancer in the organs affected by AIS. This means that the risk factors depend on the type of AIS.

However, there is one risk factor that all types of AIS have in common: Smoking increases your risk of AIS and all types of cancer.

Specific risk factors for each type of AIS are listed below.

Cervical AIS risk factors

  • HPV infection
  • untreated HPV-16 or HPV-18 infection
  • compromised immune system
  • HIV
  • smoking

Lung AIS risk factors

  • smoking
  • secondhand smoke
  • exposure to substances such as radon, diesel exhaust, arsenic, or asbestos
  • family history of lung cancer
  • personal history of lung cancer
  • history of radiation treatments to your chest

Pancreatic AIS risk factors

  • smoking
  • using smokeless tobacco products
  • diabetes
  • obesity
  • family history of pancreatic cancer
  • inherited gene mutations
  • chronic pancreatitis
  • exposure to chemicals used in cleaning and metalwork
  • being over age 45

Colon AIS risk factors

  • smoking
  • heavy alcohol use
  • eating a diet that is high in fat and low in fiber
  • not getting enough physical exercise
  • obesity
  • history of chronic conditions of your intestines or colon, such as irritable bowel syndrome (IBS) or Crohn’s disease
  • family history of colon cancer
  • inherited genetic mutations
  • personal history of colon cancer or polyps
  • history of radiation treatments to your stomach
  • diabetes
  • being over age 50

The good news is that AIS is very treatable. The goal of treatment is to remove the abnormal cells before they turn into cancerous cells. This is done by surgically removing the cells or tumor. This type of surgery can often be done by laparoscopy.

Doctors perform laparoscopic surgery by inserting a small camera into your body to help them see your organs and the tumor. This allows them to make only a small incision. Laparoscopic surgeries are less invasive and have shorter healing times than traditional surgeries.

Cervical AIS treatment

Treatment for most types of AIS involves simply removing the AIS tumor, but treatment for cervical AIS is a little different. Your treatment for cervical AIS depends on a few different factors.

The first step will be to remove the abnormal cells through a procedure called excision. Following the excision, you and your doctor will need to make some decisions.

Often, doctors will also perform a hysterectomy to prevent cervical cancer from returning. However, if you wish to become pregnant in the future, you’ll need to go a different route.

In this case, you’ll have frequent testing to ensure you aren’t developing more abnormal cells. This testing will include pap smears, HPV testing, and endocervical tissue biopsies.

For many people with cervical AIS, this is a complex decision. It’s important to talk it over thoroughly with your doctor to make sure you understand all the risks and benefits of your decision. You and your doctor can work together to look at all the possible outcomes and make the best choice for you.

AIS is a form of cancer that’s caught extremely early in its growth process. When someone has AIS, their abnormal cells haven’t become cancerous yet and aren’t causing symptoms.

This early detection is why AIS has an excellent outlook. When AIS is treated, the cells never become cancerous and you can make a full recovery.

AIS can occur in any organ with mucus-producing glands. It is typically found in the cervix, pancreas, lungs, and colon.

AIS doesn’t cause any symptoms and is normally found during routine screening or imaging tests for other conditions.

AIS is treated by removing the abnormal cells before they become cancer. A person with AIS can recover completely as long as they are treated quickly and thoroughly.