There are two very important things to know about neoplasms of the pancreas. First, some, such as the "intraductal papillary mucinous neoplasm," are curable precancerous lesions. Just as colon cancer arises from curable precancerous colon polyps, so to do some pancreatic cancers arise from curable precancerous lesions.
Second, as we alluded to earlier, a variety of different types of neoplasms can arise in the pancreas, such as ductal adenocarcinoma and pancreatic neuroendocrine tumor, and these different tumor types are important to recognize because they are often treated differently, and because they are associated with different prognoses (predicted outcomes).
Trained expert pathologists usually establish the diagnosis of a specific type of neoplasm. They do this either from biopsies of the tumor or by examining resected (removed) tumors.
This is the form of cancer that most people are talking about when they refer to "cancer of the pancreas." These neoplasms account for >75% of all pancreas cancers.
Adenocarcinomas (most common) - Just as the normal exocrine cells of the pancreas do, adenocarcinomas form microscopic glands (collections of cells surrounding an empty space). Adenocarcinomas can grow large enough to invade nerves which can cause back pain. They also frequently spread (metastasize) to the liver or lymph nodes. If this happens the tumor may be considered unresectable.
Adenocarcinoma: This is a gland-forming (it makes tubes) cancer.
In this example, the adenocarinoma has wrapped around a nerve (center of the image).
The following rare exocrine neoplasms of the pancreas are listed alphabetically.
Acinar Cell Carcinomas - These rare cancers may produce excess amounts of the digestive enzymes normally produced by the pancreas. This increase in enzymes causes distinct symptoms in 20% of patients with an acinar cell carcinoma. These symptoms may include unusual skin rashes, joint pain and an increased number of eosinophils, a type of white blood cell, in the blood.
Microscopically, the cytoplasm of the cancerous cells in acinar cell carcinoma has a characteristic granular appearance. This is because the cancerous cells contain large amounts of a cell organelle called the zymogen granule. Special tests performed by pathologists on microscope slides, including immunohistochemistry, can often be used to diagnose this type of cancer.
Adenosquamous Carcinomas - This rare variant of pancreatic cancer is similar to adenocarcinoma because it also forms glands. These cancers also show a second component, "squamous differentiation." This means that the cells tend to flatten out as they grow.
This variant of pancreatic cancer is important to recognize because it is associated with a particularly poor prognosis, and in some instances is treated differently.
Colloid Carcinomas - Colloid carcinoma is a distinctive cancer of the pancreas associated with a better prognosis than the more common ductal adenocarcinoma. Under the microscope small nests of cancer cells appear to be "floating" in pools of extracellular mucin. Many colloid carcinomas arise in association with another type of tumor, the intraductal papillary mucinous neoplasm (IPMN) of the pancreas.
Hepatoid Carcinomas - Hepatoid carcinomas of the pancreas have been reported only extremely rarely in the pancreas. Under the microscope, the cells that form this type of cancer look like the cells of a liver cancer (hepatoid means liver-like).
Intraductal Papillary Mucinous Neoplasms - These neoplasms are also known as "IPMNs." They are important to recognize because they represent a potentially curable precursor lesion to invasive pancreatic cancer. IPMNs characteristically grow in the larger ducts of the pancreas (hence the name "intraductal!").
Under the microscope they usually appear as finger-like structures (papillae, hence the name papillary) projecting into the pancreatic duct. IPMNs are believed to start as curable precancerous lesions, and some, if untreated, may progress to invasive adenocarcinomas.
Mucinous Cystic Neoplasms - This is a rare, cystic (containing collections of fluid), neoplasm of the pancreas. Most are found in the tail of the pancreas in women. The spaces within this neoplasm are filled with a thick fluid called mucin. Unlike the serous cystadenomas (see below), these neoplasms can progress into an invasive cancer over time.
Pancreatic Intraepithelial Neoplasia - Pancreatic intraepithelial neoplasia- A small microscopic (the size of the head of a pin) precancerous lesion in the pancreas. These are also called "PanINs" and are too small to be detected using currently available imaging technologies. They are, however, a very active area of research as some scientists believe they may hold the clue to the early detection of pancreatic cancer. If left untreated, some PanINs will progress over years to invasive ductal adenocarcinoma.
Pancreatoblastomas - These rare malignant neoplasms predominantly occur in children. The reason for this is unknown. These cancers are also referred to as the "pancreatic cancer of infancy."
Microscopically, pancreatoblastomas appear as nests of flat (squamoid) cells floating in a sea of more uniform cells. The cells of pancreatoblastomas can also show acinar differentiation and endocrine differentiation.
Serous Cystadenomas - These rare tumors are usually benign (noncancerous) growths. However, they can grow to be quite large and may need to be surgically removed if symptoms such as pain and weight loss occur. They are cystic, fluid containing, tumors with a sponge-like appearance.
Serous cystadenoma: This benign tumor forms spaces (cysts), giving the tumor a "sponge-like" appearance.
Signet Ring Cell Carcinoma - This rare form of pancreatic cancer has a characteristic microscopic appearance. Signet ring cell carcinomas are composed of individual cells with a large mucin globule. This mucin globule pushes the nucleus of the cell to the side, giving the cell a "signet" or ring-like appearance.
Solid-Pseudopapillary Neoplasm - These rare neoplasms occur primarily in women in their 30's. As the name implies some parts of the neoplasms are solid and some are papillary (form finger-like projections). Solid-pseudopapillary neoplasms are considered low-grade cancers, but they have a very good prognosis. Since they can spread to other organs they should be removed completely.
Solid-pseudopapillary neoplasm: This is a smear made by touching a microscope slide to the surface of the tumor.
The center star-shaped structure is composed of thin delicate blood vessels (the lines radiating out) with
small tumor cells clinging on to the outside surface of the blood vessels.
Undifferentiated Carcinomas - Undifferentiated carcinoma is an extremely aggressive form of pancreatic cancer that lacks a direction of differentiation. This means that under the microscope these cancers do not resemble any normal cell type in the body.
Undifferentiated Carcinoma with Osteoclast-like Giant Cells - These cancers are extremely rare. As the name "undifferentiated carcinomas with osteoclast-like giant cells" indicates, these cancers have unusually large "giant" cells. This does not mean that the cancer itself is larger than other types of cancer, only that individual cells in this form of cancer are so unusually large that they look like some very large cells (osteoclasts) found in the normal bone.
Undifferentiated carcinoma with osteoclast-like giant cells: This tumor is composed of two cell types.
The cancerous cells are the big cells on the right of this image. The large osteoclast-like cells (center of the image)
contain lots of nuclei and are the body's non-tumorous cells reacting to the cancer.
Neuroendocrine Tumors - These neoplasms are far less common than the exocrine neoplasms listed above. Neuroendocrine neoplasms (also known as endocrine or islet cell tumors) account for about 1-5% of pancreatic cancers. It is very important that endocrine neoplasms be distinguished from nonendocrine because the symptoms and the treatments for the two neoplasms are very different.
The neuroendocrine neoplasms may produce highly active hormones and therefore have very dramatic symptoms.
There are different kinds, including:
Insulinomas produce large amounts of the hormone insulin which can result in hypoglycemia ( low blood sugar).
Glucagonomas produce the hormone glucagon which can result in a very striking skin rash (necrolytic migratory erythema.)