By Jason Wasserman MD PhD FRCPC
January 28, 2025
A solid pseudopapillary neoplasm is a rare type of tumour that starts in the pancreas. The pancreas is an organ in your abdomen that helps with digestion and regulates blood sugar levels. This tumour gets its name from the way it looks under the microscope, with solid areas and more loose or papillary (finger-like). It is most often found in young women and tends to grow slowly.
Many people with this tumour do not have symptoms at first. When symptoms do appear, they may include:
Sometimes, these symptoms are caused by the tumour pressing on nearby organs.
The exact cause of this tumour is not fully understood, but several factors may play a role:
These factors may explain why and how this tumour occurs, but more research is needed to fully understand its causes.
This tumour is considered a low grade malignant neoplasm. This means it has some features of cancer but behaves much less aggressively than most types of cancer. Most people with this tumour have an excellent prognosis, especially if the tumour is completely removed with surgery.
After removing a sample, a tumour is examined under a microscope to confirm the diagnosis. Pathologists, who study tissues and cells, look for certain features to confirm the diagnosis. They may also use special tests, such as immunohistochemistry, to gather more information about the tumour.
Under the microscope, this tumour has solid (dense) areas and pseudopapillary (loose and finger-like) areas. It often contains areas of bleeding (hemorrhage) and spaces filled with fluid (pseudocysts). The tumour cells are round and do not stick tightly to each other. They form structures around thin blood vessels called fibrovascular stalks.
Pathologists may also see:
The tumour is usually well-defined but can sometimes grow into the nearby pancreas tissue. Features like invasion into blood vessels or nerves are rare. The tumour cells contain pink or clear material, and their nuclei (the part of the cell that contains DNA) may look grooved or irregular. Mitoses, or signs of cell division, are uncommon.
Immunohistochemistry is a test that uses special stains to identify proteins in the tumour cells. These stains help pathologists confirm the diagnosis and rule out other tumours.
For solid pseudopapillary neoplasms, the tumour cells usually show:
These tests are important because other tumours, like neuroendocrine tumours or acinar cell carcinomas, can look similar under the microscope.
Perineural invasion occurs when cancer cells are found inside or around nerves. Nerves transmit signals, such as pain or temperature, between the body and the brain. Cancer cells can use nerves to spread to surrounding tissues, increasing the risk of tumour recurrence after surgery.
Lymphovascular invasion means cancer cells are found inside blood vessels or lymphatic vessels. Blood vessels carry blood throughout the body, while lymphatic vessels carry a fluid called lymph to small immune organs called lymph nodes. Cancer cells can use these vessels to spread to other body parts, such as lymph nodes or distant organs.
Margins refer to the edges of tissue removed during surgery. A negative margin means no cancer cells are found at the edge, while a positive margin means cancer cells are at the cut edge. Positive margins suggest that some cancer may have been left behind, and additional treatment, such as surgery or radiation therapy, may be needed.
Key margins in the pancreas include:
The pathologic stage for solid pseudopapillary neoplasm of the pancreas is determined using the TNM system, which stands for Tumour (T), Nodes (N), and Metastases (M). Each category is assigned a number:
Tumour stage (pT):
Nodal stage (pN):
The prognosis for this tumour is excellent for most people, even if the tumour has spread to other parts of the body. Surgery to remove the tumour is the primary treatment, and most patients remain disease-free for many years after surgery.
In rare cases, the tumour may behave more aggressively and spread. This is more likely if the tumour contains an undifferentiated (less organized) component. While features like invasion into nearby structures or blood vessels can occur, they do not always predict whether the tumour will spread.
Factors that may be linked to a worse prognosis include:
Even in these cases, the tumour generally grows slowly, and treatment can often control the disease for a long time.