Your pathology report for pancreatic intraepithelial neoplasia (PanIN)

by Jason Wasserman MD PhD FRCPC
July 29, 2025

Pancreatic intraepithelial neoplasia, or PanIN, is a microscopic-sized growth that starts in the small ducts of the pancreas. It is not cancer, but it is considered a type of precancerous change. This means that over time, PanIN can turn into a type of pancreatic cancer called ductal adenocarcinoma.

PanIN is only visible under the microscope and is usually discovered incidentally when the pancreas is examined for another reason, such as after surgery for a tumor or another pancreatic condition.

What causes PanIN?

The exact cause of PanIN is not known, but several factors are believed to increase the risk. These include:

  • Older age.

  • Obesity.

  • Diabetes.

  • Chronic inflammation of the pancreas (pancreatitis).

  • A family history of pancreatic cancer.

PanIN is also more common in people with inherited genetic conditions that increase the risk of pancreatic cancer.

Where in the pancreas is PanIN found?

PanIN can be found anywhere in the pancreas but is most commonly seen in the head of the pancreas. In people with a family history of pancreatic cancer, PanIN may be present in multiple areas of the pancreas at the same time.

What genetic changes are found in PanIN?

Doctors have found that PanIN often contains genetic mutations, especially in genes involved in cancer development. One of the most common mutations is in a gene called KRAS, which is found in more than 90% of PanIN lesions. Other genes that may be affected, especially in high grade dysplasia, include CDKN2A (also called P16). These changes accumulate gradually over many years and may eventually lead to cancer if not interrupted.

How is this diagnosis made?

Because PanIN is a microscopic change, the diagnosis can only be made by a pathologist examining tissue from the pancreas under the microscope. In most cases, this tissue is obtained during surgery to remove part or all of the pancreas. It is not typically detected by imaging or needle biopsy before surgery.

What does PanIN look like under the microscope?

Under the microscope, PanIN involves small ducts in the pancreas that are lined by abnormal cells. These cells may be flat, tall, or arranged in small finger-like projections. The cells produce mucin, a sticky substance normally made by glands in the body. In some cases, the ducts may appear slightly enlarged or surrounded by changes in the surrounding tissue, including inflammation or scarring.

Low grade versus high grade dysplasia in PanIN

PanIN is a type of dysplasia. Dysplasia is a word pathologists use to describe abnormal cells that are still confined to the layer of tissue where they started. Dysplasia is not cancer, but it can become cancer over time. PanIN is divided into two grades based on how abnormal the cells look under the microscope.

Low grade dysplasia

In low grade dysplasia, the cells lining the ducts are only mildly abnormal. The cells may be crowded, and their nuclei (the part of the cell that contains DNA) may be slightly larger or darker than normal. PanIN with low grade dysplasia is very common, especially in people over the age of 50. It is often found incidentally and does not usually require treatment.

High grade dysplasia

In high grade dysplasia, the cells look much more abnormal. They may be very irregular in shape, overlap one another, and show signs of rapid division. High grade dysplasia is considered a more advanced precancerous change and may be associated with a higher risk of developing invasive cancer. In some cases, high grade PanIN may be a warning sign of cancer elsewhere in the pancreas.

What does it mean if PanIN is found at the margin?

If PanIN is found at the margin (the edge of the tissue removed during surgery), it means that some abnormal cells may remain in the body. This is usually not a concern for low grade dysplasia. However, if high grade dysplasia is found at a margin and there is no invasive cancer, your doctor may consider additional treatment to reduce the risk of developing cancer in the future.

If an invasive cancer is already present, the finding of PanIN at the margin does not usually change the treatment or prognosis.

What stage is PanIN?

Only high grade PanIN is assigned a stage. It is classified as stage Tis, which means carcinoma in situ. This means the abnormal cells have not invaded surrounding tissues and remain confined to the ducts. Low grade PanIN is not given a stage because it is not considered a direct threat to health.

How is PanIN different from IPMN?

PanIN and intraductal papillary mucinous neoplasm (IPMN) are both precancerous conditions that start in the ducts of the pancreas. However, there are some important differences:

  • PanIN is very small (usually less than 0.5 cm) and can only be seen under the microscope.

  • IPMN is larger (usually greater than 1 cm) and often forms cysts or papillary (finger-like) projections that can be seen on imaging studies.

  • IPMN can have different subtypes, while PanIN usually shows gastric-type features.

Lesions between 0.5 and 1.0 cm are sometimes called “incipient IPMN” if they have intestinal or oncocytic features.

What is the prognosis for a person with PanIN?

The prognosis for a person diagnosed with PanIN depends on the grade of dysplasia:

  • Low grade PanIN is common and not considered harmful. It does not usually require treatment or follow-up.

  • High grade PanIN is less common and may be associated with a higher risk of developing cancer. If high grade PanIN is found during surgery, your doctor may recommend close follow-up or additional treatment, especially if no invasive cancer has yet been found.

PanIN by itself does not usually cause symptoms, and most people with PanIN will never develop pancreatic cancer. However, in some cases, PanIN can serve as a warning sign and may help doctors identify people at higher risk of developing cancer in the future.

Questions to ask your doctor

  • Was the PanIN found in the area of cancer or somewhere else?

  • What grade of dysplasia was seen?

  • Was PanIN found at the surgical margin?

  • Is there any evidence of invasive cancer?

  • Will I need further treatment or follow-up?

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