Pancreatic Intraepithelial Neoplasia (PanIN): Understanding Your Pathology Report

by Jason Wasserman MD PhD FRCPC
June 15, 2026

Pancreatic intraepithelial neoplasia, or PanIN, is a microscopic growth that starts in the small ducts of the pancreas. It is not cancer, but it is considered a precancerous change, which means that over many years it can sometimes turn into a type of pancreatic cancer called ductal adenocarcinoma. PanIN is too small to be seen on imaging or felt during an examination and causes no symptoms. It is almost always discovered by chance when the pancreas is examined under the microscope for another reason, such as after surgery for a tumor or another pancreatic condition. Most people with PanIN will never develop pancreatic cancer.

This article will help you understand the findings in your pathology report, what each term means, and why it matters for your care.

What causes PanIN?

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

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 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 often seen in the head of the gland. In people with a family history of pancreatic cancer, PanIN may be present in several areas of the pancreas at the same time.

How is the diagnosis made?

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

Under the microscope, PanIN involves small ducts lined by abnormal cells. These cells may be flat, tall, or arranged in small finger-like projections, and they produce mucin, a sticky substance normally made by glands in the body. The affected ducts may look slightly enlarged, and the surrounding tissue may show inflammation or scarring. At the genetic level, PanIN often carries changes in a gene called KRAS, found in more than 90 percent of these lesions, and additional changes, such as in the CDKN2A (also called P16) gene, may appear in high grade PanIN. These changes build up gradually over many years and may eventually lead to cancer if the process is not interrupted.

Grade (degree of dysplasia)

PanIN is a type of dysplasia, a word pathologists use for 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:

Low grade dysplasia — The cells lining the ducts are only mildly abnormal. They may be crowded, and their nuclei (the part of the cell that contains DNA) may be slightly larger or darker than normal. Low grade PanIN is very common, especially in people over the age of 50. It is usually found by chance and does not require treatment.
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 PanIN is a more advanced precancerous change and carries a higher risk of progressing to invasive cancer. It can also be a sign of cancer elsewhere in the pancreas.

High grade PanIN is also called carcinoma in situ and may appear on a report as stage Tis, which means the abnormal cells have not invaded the surrounding tissue and remain confined to the ducts. Low grade PanIN is not given a stage because it is not considered a direct threat to health. You may also see the older terms PanIN-1, PanIN-2, and PanIN-3 on some reports; in the current two-grade system, PanIN-1 and PanIN-2 are grouped as low grade, and PanIN-3 is the same as high grade.

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

A margin is the edge of the tissue removed during surgery. If PanIN is found at the margin, it means some abnormal cells may remain in the pancreas. For low grade PanIN, this is usually not a concern. If high grade PanIN is found at a margin and there is no invasive cancer, the treatment team may consider closer follow-up or additional treatment to lower the risk of cancer developing in the future. When invasive cancer is already present, finding PanIN at the margin usually does not change treatment or outlook.

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, but they differ in important ways:

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 finger-like projections that can be seen on imaging.
IPMN has several cell subtypes, whereas PanIN typically exhibits gastric-type features.

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

What is the prognosis?

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

Low grade PanIN — Common and not considered harmful. It does not usually require treatment or follow-up.
High grade PanIN — Less common, and linked to a higher risk of developing cancer. If it is found during surgery, the treatment team may recommend close follow-up or additional treatment, especially when no invasive cancer has been found.

PanIN by itself does not cause symptoms, and most people with PanIN will never develop pancreatic cancer. In some cases, however, PanIN serves as a warning sign that can help doctors identify people at higher risk who may benefit from closer monitoring.

What happens after the diagnosis?

What happens next depends mostly on the grade of dysplasia and on whether PanIN was found on its own or alongside another pancreatic condition. Low grade PanIN found by chance usually requires no specific treatment or additional follow-up. High grade PanIN, particularly when it reaches a surgical margin and no invasive cancer is present, may lead the team to consider closer surveillance of the remaining pancreas. When PanIN is found next to an invasive cancer, care is guided by the cancer rather than by the PanIN. If an inherited condition that raises pancreatic cancer risk is suspected, your doctor may suggest genetic counseling, which can also help relatives understand their own risk.

Questions to ask your doctor

Was the PanIN found in the area of a cancer or somewhere else in the pancreas?
What grade of dysplasia was seen, low grade or high grade?
Was PanIN found at the surgical margin?
Is there any evidence of invasive cancer?
Does this finding change my risk of developing pancreatic cancer?
Will I need any further treatment?
Will I need follow-up imaging or monitoring, and how often?
Should I consider genetic counseling for myself or my family?