Understanding Neuroendocrine Tumors in Practice

Neuroendocrine tumors (NETs), while historically considered rare, are increasingly recognized in clinical practice due to advancements in diagnostic techniques and greater awareness. Though their incidence remains relatively steady, the prevalence has grown significantly over recent decades. These tumors most commonly originate in the small bowel, lungs, and pancreas, though they can arise throughout the body. Due to this wide range of potential origins, it's essential for clinicians to be familiar with their diverse presentations. NETs often remain undiagnosed for years, in part because their symptoms—such as flushing and diarrhea—can mimic those of far more common conditions.

Clinically, NETs are unique in that they can cause both tumor-related and hormone-related symptoms. Tumor-related symptoms may include pain, bowel obstructions, bleeding, or bile duct compression, depending on the tumor’s location and size. On the other hand, hormone-related symptoms, particularly in functional tumors, are tied to excess hormone secretion and may involve carcinoid syndrome (eg, flushing, diarrhea, bronchospasm) or effects from hormone overproduction in pancreatic NETs, such as insulin, glucagon, ACTH, or calcitonin. Because of this wide symptom spectrum, NETs are often called “great masqueraders,” and many patients experience significant diagnostic delays.

NETs not only captivate interest due to their complex presentation but are also becoming a growing clinical concern. The increasing prevalence now places them among the most common gastrointestinal cancers, second only to colorectal cancer in some European data. Personal experiences often fuel interest in the field, such as a striking clinical moment involving a visible carcinoid reaction in a patient, which highlighted the distinctiveness of these tumors. These real-world experiences, combined with the scientific intricacies of the disease, continue to draw attention to NETs as a critical area of oncologic care.