PANCE Blueprint Pulmonary (9%)

Patient will present with → a 38-year-old nonsmoking woman who comes to the clinic with a persistent cough and recurrent pneumonia in the same lobe (the right middle lobe, three times in the past year), along with several episodes of blood-streaked sputum. She was told she has asthma, but inhalers have not helped. She denies flushing or diarrhea. On physical examination, there is a localized, fixed wheeze over the right mid-lung field. Chest CT reveals a well-circumscribed central endobronchial mass in the right middle lobe bronchus with post-obstructive atelectasis. Bronchoscopy shows a smooth, pink-purple, highly vascular lesion, and biopsy confirms a typical carcinoid tumor (chromogranin A positive).

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"Symptoms of carcinoid syndrome can be memorized using the mnemonic FDR (flushing, diarrhea, and right-sided heart valves)."

A tumor arising from neuroendocrine cells → leading to excess secretion of serotonin, histamine, and bradykinin

• Common primary sites include GI (small and large intestines, stomach, pancreas, liver), lungs, ovaries, and thymus
  • The most common site for a neuroendocrine (carcinoid) tumor to metastasize to is the liver
  • The small intestine (ileum) is the most common source of carcinoid syndrome, which appears once the tumor has spread to the liver; lung carcinoids are usually primary bronchial tumors, not metastases from the gut
• Usually asymptomatic until liver metastasis; symptoms develop occasionally
  • GI tract tumor→ hormone secretion → enter the portal circulation → liver inactivates hormones → no symptoms
  • Liver tumor → hormone secretion → released into circulation + liver dysfunction → symptoms
• Carcinoid syndrome (the hallmark sign) = Cutaneous flushing, diarrhea, wheezing and low blood pressure is actually quite rare and occurs in ~ 5% of carcinoid tumors and becomes manifest when vasoactive substances from the tumors enter the systemic circulation, escaping hepatic degradation.
• The syndrome includes flushing, ↑ intestinal motility (diarrhea), itching and less frequently, heart failure, vomiting, bronchoconstriction, asthma, and wheezing
  • ↑ Serotonin leads to collagen fiber thickening, fibrosis = heart valve dysfunction → tricuspid regurgitation, pulmonary stenosis/bronchoconstriction, and wheezing
  • ↑ Histamine and bradykinin = vasodilation and flushing
  • ↑ serotonin synthesis → ↓ tryptophan → ↓ niacin/B3 synthesis = pellagra

CT-Scan to locate the tumors

• Somatostatin receptor imaging (Ga-68 DOTATATE PET, which has replaced the older Octreoscan) → a radiolabeled somatostatin analog binds to somatostatin receptors on tumor cells
• 24-hour urine 5-hydroxyindoleacetic acid (5-HIAA) → the main metabolite of serotonin; best initial test when carcinoid syndrome is suspected (it can be normal with bronchial carcinoids)
• Pellagra (niacin/B3 deficiency) - ↑ serotonin synthesis → ↓ tryptophan → ↓ niacin/B3 synthesis
• CT of the chest shows a well-circumscribed central endobronchial mass, often with post-obstructive atelectasis or pneumonia
• Bronchoscopy with biopsy confirms the diagnosis: a pink/purple, well-vascularized central lesion

Carcinoid tumors are usually centrally located, arising in large airways. The arrow points to the tumor in the right hilar region. Image: Yale Rosen from USA, CC BY-SA 2.0, via Wikimedia Commons.

Treatment is by surgical excision and carries a good prognosis

• The lesions are relatively resistant to radiation therapy and chemotherapy
• Octreotide or lanreotide - somatostatin analogs that bind somatostatin receptors and decrease the secretion of serotonin by the tumor, controlling carcinoid syndrome symptoms
• Niacin supplementation