Neoplasia: carcinoid syndrome: practice question

A Pathology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Pathology · Neoplasia: carcinoid syndrome

Sample item

A 55-year-old man with an ileal carcinoid tumour and multiple liver metastases has flushing, watery diarrhoea and wheeze. Echocardiography shows tricuspid regurgitation and pulmonary stenosis. Why does the syndrome appear only with liver metastases, and which test confirms it?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

A. Serotonin from hepatic metastases bypasses first-pass hepatic metabolism; urinary 5-HIAA is raised

Gastrointestinal carcinoids drain through the portal vein, where the liver degrades serotonin, so syndrome is absent unless liver metastases drain directly into the hepatic veins. Serotonin is metabolised to 5-hydroxyindoleacetic acid, measured in a 24-hour urine collection. Fibrous plaques on the right-sided valves cause tricuspid regurgitation and pulmonary stenosis because the lungs inactivate serotonin.

Option by option

  • A. Serotonin from hepatic metastases bypasses first-pass hepatic metabolism; urinary 5-HIAA is raised (correct)

    Hepatic metastases release serotonin beyond hepatic metabolism, and its metabolite 5-HIAA is raised in urine.

  • B. Serotonin from the primary tumour reaches the systemic circulation unchecked; urinary VMA is raised

    Serotonin from the primary tumour is cleared in the liver, and VMA is a catecholamine metabolite used for neuroblastoma and phaeochromocytoma.

  • C. Liver metastases secrete catecholamines into hepatic veins; urinary metanephrines are raised

    Catecholamine secretion and metanephrines indicate phaeochromocytoma, which presents with paroxysmal hypertension.

  • D. Liver metastases release gastrin causing acid hypersecretion; serum gastrin is raised

    Gastrin excess describes Zollinger-Ellison syndrome from a gastrinoma, with peptic ulceration.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Pathology question

What is the answer to this Pathology question?

The best answer is A, Serotonin from hepatic metastases bypasses first-pass hepatic metabolism; urinary 5-HIAA is raised. Gastrointestinal carcinoids drain through the portal vein, where the liver degrades serotonin, so syndrome is absent unless liver metastases drain directly into the hepatic veins.

Why is "Serotonin from the primary tumour reaches the systemic circulation un…" not the answer?

Serotonin from the primary tumour is cleared in the liver, and VMA is a catecholamine metabolite used for neuroblastoma and phaeochromocytoma.

Why is "Liver metastases secrete catecholamines into hepatic veins; urinary m…" not the answer?

Catecholamine secretion and metanephrines indicate phaeochromocytoma, which presents with paroxysmal hypertension.

Why is "Liver metastases release gastrin causing acid hypersecretion; serum g…" not the answer?

Gastrin excess describes Zollinger-Ellison syndrome from a gastrinoma, with peptic ulceration.

What concept does this question test?

It tests Neoplasia: carcinoid syndrome in Pathology. Serotonin is metabolised to 5-hydroxyindoleacetic acid, measured in a 24-hour urine collection. Fibrous plaques on the right-sided valves cause tricuspid regurgitation and pulmonary stenosis because the lungs inactivate serotonin.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Neoplasia: carcinoid syndrome?

Learn each disease as a bundle: cause, key histology, markers, and the clinical hallmark. Then use the flashcards and the other Pathology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.