Types of Pancreatic Cancer

November 22, 2024

This page was reviewed under our medical and editorial policy by Laleh Melstrom, M.D., M.S., associate professor of surgery and immuno-oncology, Division of Surgical Oncology, Department of Surgery, City of Hope^® Cancer Center Duarte

The pancreas is an abdominal organ that makes digestive enzymes and hormones, such as insulin. Pancreatic cancer develops when cells in the pancreas begin to grow uncontrollably.

These cancers are grouped into two main types — exocrine and neuroendocrine — and there are different subgroups of cancer within these two types. Exocrine pancreatic cancer is more common than neuroendocrine pancreatic cancer.

Because their risk factors, symptoms and treatments differ, it’s important to understand which type of pancreatic cancer a person has and how it affects prognosis.

Exocrine Pancreatic Cancer

Exocrine cells in the pancreas make digestive enzymes. These enzymes are secreted into the small intestine where they help to digest food. Exocrine pancreatic cancer forms when the exocrine cells grow out of control.

Pancreatic Adenocarcinoma

Adenocarcinomas make up about 95% of all exocrine pancreatic cancers. This type of cancer typically begins in tubes, or ducts, of the pancreas that secrete fluids, including digestive juices and mucus.

Other Types of Exocrine Tumors

Other types of exocrine pancreatic tumors are rare. They include those listed below.

Acinar cell carcinomas: These start to grow in the cells that produce pancreatic enzymes. They account for 0.5% to 1% of all pancreatic cancers.

Squamous cell carcinomas: This is a very rare type of exocrine pancreatic cancer that forms in the ducts of the pancreas. These tumors are made up of squamous cells, flat cells that resemble fish scales under a microscope.

Adenosquamous carcinomas: This is a type of pancreatic cancer with characteristics of adenocarcinoma and squamous cell carcinoma. It makes up between 0.38% and 10% of all exocrine pancreatic cancers..

Colloid carcinomas: These tumors may arise from a benign cyst known as an intraductal papillary mucinous neoplasm (IPMN). They represent 1% to 3% of exocrine pancreatic cancers.

Signet ring cell carcinomas: This rare adenocarcinoma makes up fewer than 1% of all exocrine pancreatic cancers.

Pancreatoblastoma: This rare cancer affects children and infants and accounts for fewer than 1% of all pancreatic cancers.

Neuroendocrine Pancreatic Cancer

Neuroendocrine pancreatic cancer, also known as pancreatic neuroendocrine tumors (NETs), starts in the islet cells of the pancreas. The islet cells make hormones, such as glucagon and insulin, which are then released into the bloodstream. Neuroendocrine pancreatic cancer accounts for less than 2% of all pancreatic cancers. It is less common than adenocarcinoma and is more responsive to treatments.

Neuroendocrine pancreatic cancer may be classified by tumor grade and function.

Tumor grade tells how fast the cancer may grow and spread to other parts of the body. Three grades are used to describe pancreatic NETs, as listed below.

Grade 1: Also known as low-grade or well-differentiated, the cells in these tumors resemble normal cells and are not fast-growing.

Grade 2: Also called intermediate-grade or moderately differentiated, the cells in these tumors have characteristics of Grade 1 and Grade 3.

Grade 3: Also known as high-grade or poorly differentiated, the cells in these tumors appear abnormal and are fast-growing. They may spread quickly to other parts of the body.

Tumor function describes whether the NETs produce symptom-causing hormones. There are two types listed below.

Functioning pancreatic NETs: These make hormones that cause symptoms.

Non-functioning pancreatic NETs: These do not make hormones and do not cause symptoms. As such, they may reach a large size before they are discovered. They may cause belly pain, as well as loss of appetite and weight.

Functioning pancreatic NETs take their names from the hormones they produce. An estimated 70% of functioning pancreatic NETs are insulinomas, which arise from cells that produce insulin. Less common types of functioning pancreatic NETs include those that arise from cells that make:

• Glucagon, known as glucagonomas
• Gastrin, known as gastrinomas
• Somatostatin, known as somatostatinomas
• Vasoactive intestinal peptide (VIP), known as VIPomas
• Adrenocorticotropic hormone (ACTH), known as ACTH-secreting tumors

Pancreatic NETs may also be classified as carcinoid tumors. These tumors are more common in other areas of the digestive system, but they may also begin growing in the pancreas. They often produce the hormone serotonin.

Benign and Precancerous Pancreatic Cysts

The term pancreatic cyst refers to a range of growths containing fluid, from the benign (noncancerous) to the potentially precancerous, as detailed below.

Simple cysts: These tend to be small and typically require no treatment. They are sometimes referred to as retention cysts.

Serous cystadenomas: These may be classified as macrocystic or microcystic, based on how the cells look under a microscope. Microcystic serous cystadenomas have a honeycomb-shaped appearance, while macrocystic serous cystadenomas resemble other types of pancreatic lesions in appearance.

Mucinous cystic neoplasms (MCNs): These cysts are thought to be linked with estrogen and progesterone and mainly affect middle-aged females. About 15% to 30% become malignant.

Intraductal papillary mucinous neoplasms (IPMNs): These typically affect older men and pose a risk for cancer if left untreated. About 20% of IPMNs are found in people with acute pancreatitis.

Pseudocysts: Usually arising from pancreatitis, these fluid-filled sacs differ from “true” pancreatic cysts because they lack a lining of epithelial cells (cells similar to the inner layer of the intestines). These cysts do not turn malignant, so a patient’s treatment plan typically depends upon the presence and severity of symptoms.

At City of Hope, doctors work with patients and their families to develop personalized treatment plans for each type of pancreatic cancer, based on its location and stage, as well as the patient’s overall health and preferences. In addition, City of Hope personalizes pancreatic cyst management using state-of-the-art imaging, molecular markers and cyst fluid analyses.