FUNCTIONAL VS NONFUNCTIONAL NEUROENDOCRINE TUMORS

Nonfunctional tumors may delay diagnosis

Neuroendocrine tumors (NET) are broadly divided into 2 subgroups based on their symptoms¹:

• Nonfunctioning tumors—no specific clinical syndrome is observed
• Functioning tumors—the tumors' secretions lead to clinical symptoms

In earlier stages of the disease, NET patients have nonfunctioning tumors or exhibit nonspecific symptoms.²

Nonfunctioning tumors may present with either no signs of the disease or only vague symptoms.³ This makes it difficult to diagnose NET at an early stage, and patients are often initially misdiagnosed with other gastrointestinal disorders, such as irritable bowel syndrome.² Correct diagnosis is typically delayed by several years.⁴

NET can progress regardless of functional status. The tumors are slow growing and may be present for years without overt symptoms, and thus escape attention.²

Functional disease and diagnosis

Once NET have metastasized, they can release a large concentration of peptide hormones and bioactive substances into the bloodstream, leading to the distinct clinical symptoms associated with functioning NET.⁴

Correct diagnosis is often made after patients develop symptoms.^2,4

50% of all patients have distant metastases at diagnosis.⁵

Carcinoid syndrome

The distinct set of symptoms caused by the secretions of functional gastrointestinal and pancreatic NET—the most common type of NET—is referred to as carcinoid syndrome.^3,6 Patients with midgut gastrointestinal and pancreatic NET may present with carcinoid syndrome.²

Percentage of patients with symptoms of carcinoid syndrome⁷*

The most common symptoms of carcinoid syndrome are diarrhea and flushing. Additional symptoms may include abdominal pain, heart disease, and sweating.²

Flushing: red or purple coloring that appears suddenly on the face or neck; it may be accompanied by a feeling of warmth or a rapid heartbeat and is not typically associated with sweating.³