What are the symptoms of carcinoid tumors?

Symptoms of Carcinoid Tumors

Carcinoid tumors present with highly variable symptoms depending on tumor location and hormone secretion, with many patients remaining asymptomatic until metastatic disease develops, while the classic carcinoid syndrome triad of flushing, diarrhea, and cardiac involvement occurs primarily when liver metastases allow vasoactive substances to bypass hepatic metabolism. 1

Gastroenteropancreatic Carcinoid Presentations

Asymptomatic or Non-Specific Presentations

• Many primary gastroenteropancreatic tumors are completely asymptomatic and discovered incidentally during endoscopy or imaging for unrelated conditions 1
• When symptomatic without hormone secretion, patients present with obstructive symptoms including pain, nausea, and vomiting, often despite normal initial radiology 1

Classic Carcinoid Syndrome (Metastatic Disease)

The carcinoid syndrome typically occurs only after liver metastases develop, allowing serotonin, tachykinins, and other vasoactive compounds to enter systemic circulation directly without hepatic first-pass metabolism 1

At diagnosis, the frequency of symptoms in carcinoid syndrome patients is:

• Intermittent abdominal pain: 70% 1
• Diarrhea: 50% 1
• Flushing: 30% 1

Additional carcinoid syndrome manifestations include:

• Lacrymation and rhinorrhoea during flushing episodes 1
• Episodic palpitations coinciding with flushing 1
• Wheezing as a less common presenting feature 1
• Pellagra (due to tryptophan depletion for serotonin synthesis) occurring rarely 1
• Carcinoid heart disease (tricuspid and pulmonary valve involvement) typically developing only after the syndrome has been present for several years 1, 2

Bronchial Carcinoid Presentations

Bronchial carcinoids have distinctly different symptomatology:

• Bronchial obstruction symptoms (41%): obstructive pneumonitis, pleuritic pain, atelectasis, difficulty breathing 1
• Cough (35%) 1
• Hemoptysis (23%) 1
• Non-specific symptoms (15%): weakness, nausea, weight loss, night sweats, neuralgia 1
• Cushing's syndrome from ectopic ACTH secretion in rare cases 1
• Up to 30% are completely asymptomatic at presentation 1

Carcinoid Crisis (Life-Threatening Emergency)

Carcinoid crisis is characterized by:

• Profound flushing 1
• Bronchospasm 1
• Tachycardia 1
• Widely and rapidly fluctuating blood pressure 1

This emergency is precipitated by anesthetic induction, intraoperative tumor manipulation, or invasive radiological procedures due to massive release of serotonin and vasoactive peptides 1, 3. Recognition is critical as this represents an immediate threat to life requiring urgent intervention.

Pancreatic Neuroendocrine Tumor Syndromes

Different functional pancreatic NETs produce distinct symptom complexes based on hormone secretion 1:

Insulinoma symptoms:

• Confusion, sweating, dizziness, weakness, unconsciousness
• Relief with eating 1

Gastrinoma (Zollinger-Ellison syndrome):

• Severe peptic ulceration
• Diarrhea 1

Glucagonoma:

• Necrolytic migratory erythema (pathognomonic skin rash)
• Weight loss, diabetes mellitus, stomatitis, diarrhea 1

VIPoma (Werner-Morrison syndrome):

• Profuse watery diarrhea with marked hypokalemia 1

Somatostatinoma:

• Cholelithiasis, weight loss, diarrhea and steatorrhea, diabetes mellitus 1

Critical Clinical Pitfalls

Important caveats to avoid diagnostic delays:

• The prosaic symptoms of flushing, diarrhea, and sweating are frequently overlooked, leading to significant diagnostic delays and advanced disease at presentation 4
• Similar syndromes can occur even when no measurable hormones are detected in blood or urine, requiring high clinical suspicion 1
• Non-syndromic pancreatic NETs present only with symptoms from pancreatic mass effect or liver metastases without hormonal manifestations 1
• Mesenteric fibrosis can cause small bowel obstruction, bowel ischemia, or ureteral obstruction as late complications requiring monitoring 3, 5