PANCE Blueprint Pulmonary (10%)

Patient will present with → a 43-year-old man who comes to the emergency department because of a 3-week history of episodic cutaneous flushing, diarrhea, and wheezing. He has a past medical history of hypertension and type 2 diabetes mellitus. His temperature is 36.6°C (97.9°F), pulse is 125/min, respirations are 30/min, and blood pressure is 90/60 mm Hg. Pulmonary examination shows diffuse wheezes in both lung fields. Cardiac examination shows a prominent "v" wave of the jugular vein and a 1/6 holosystolic murmur best heard on the left lower sternal border. Abdominal examination shows hyperactive bowel sounds.

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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 of a neuroendocrine (carcinoid) tumor to metastasize to is the liver
  • Carcinoid tumor of the appendix is the most common cause. The appendiceal cancer travels from the appendix then to the liver where it metastasizes to the lungs
• Usually asymptomatic until liver metastasis; symptoms develop occasionally
  • GI tract tumor→ hormone secretion → enter into enterohepatic 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

• Octreoscan → radiolabeled somatostatin analog (octreotide) binds to somatostatin receptors on tumor cells
• Urinalysis → elevated 5-hydroxyindoleacetic acid (5-HIAA) → is the main metabolite of serotonin and is used to determine serotonin levels in the body
• Pellagra (niacin/B3 deficiency) - ↑ serotonin synthesis → ↓ tryptophan → ↓ niacin/B3 synthesis
• Chest X-Ray shows low-grade CA seen as pedunculated sessile growth in the central bronchi
• Bronchoscopy- pink/purple central lesion, well-vascularized

Endobronchial carcinoid tumor in a Crohn disease patient (centrally located sessile growth is common)

Treatment is by surgical excision and carries a good prognosis

• The lesions are resistant to radiation therapy and chemotherapy
• Octreotide - a somatostatin analog that binds the somatostatin receptors and decreases the secretion of serotonin by the tumor
• Niacin supplementation