PANCE Blueprint Pulmonary (9%)

Patient will present with → a 55-year-old female who comes to the clinic complaining of recurrent episodes of flushing, particularly on her face and neck, and diarrhea for the past six months. She notes that the flushing episodes last for about five minutes and are sometimes accompanied by a feeling of warmth and palpitations. Her medical history is unremarkable except for mild asthma. On physical examination, there are no abnormal findings except for slight wheezing on lung auscultation. Given her symptoms, a 24-hour urine test for 5-HIAA is ordered, which returns elevated. An abdominal CT scan reveals a small mass in the ileum and hepatic metastases.

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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
  • 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

Carcinoid tumors are usually centrally located, arising in large airways. The arrow points to the tumor in the right hilar region.

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