Introduction: Biology of Pancreatic Neuroendocrine Tumors

Sixty-eight percent of individuals with pancreatic neuroendocrine tumors (NETs) present to their physicians with metastatic disease, states Rodney Pommier, MD. These patients often have symptoms that prompt a CT scan, revealing lesions throughout the liver, says Pommier. Usually, a follow-up biopsy shows a well differentiated low-grade or intermediate-grade NET.

Carcinoid tumors typically develop slowly in the lining of the digestive tract or lungs, and it can be difficult to determine their primary origin. Most pancreatic NETs are fairly noticeable on cross-sectional imaging, such as a CT or MRI scan, notes Pommier. Historically, treatments for all NETs were quite similar, but today there is a distinction in treatments between pancreatic NETs and carcinoid tumors.

NETs can also be differentiated based on functional status. Over half of pancreatic neuroendocrine tumors are clinically nonfunctional, says Pommier. These tumors secrete a hormone that is detectable in the blood, but unless individuals suffer from a specific syndrome related to these excessive hormone levels, the tumor is clinically nonfunctional.

There are 4 classic functional tumors (gastrinomas, insulinomas, glucagonomas, and VIPomas), each of which produces problematic hormonal syndromes, explains Prommier. Gastrinomas and insulinomas may be identified when the tumors are still small and nonmetastatic, whereas glucagonomas and VIPomas are more insidious and are typically located alongside metastatic disease.

Clinicians are conflicted on how to treat patients with small, nonfunctioning tumors that were found incidentally in cross-sectional imaging, states Prommier. Textbooks currently suggest that treatment should be initiated, depending on tumor size, but obtaining a biopsy of the tumor may also be helpful, states J. Philip Boudreaux, MD. Looking at Ki-67 and mitotic index will provide information regarding whether the tumor is differentiated, moderately well differentiated, or other, explains Boudreaux. Age may also be a factor in deciding how to treat, adds Diane Reidy-Lagunes, MD.