Carcinoid tumors develop from neuroendocrine cells in the gastrointestinal tract (90%), pancreas, pulmonary bronchi, and rarely the genitourinary tract. Although carcinoids are often benign or only locally invasive, those affecting the bronchus are frequently malignant . Some carcinoid tumors are endocrinologically active; the likelihood varies by site of origin and is highest for tumors originating in the ileum and proximal colon (40 to 50%) and lower with bronchial carcinoids.
Half of patients with bronchial carcinoid are asymptomatic, and half present with symptoms of airway obstruction, including dyspnea, wheezing, and cough, which often leads to a misdiagnosis of asthma. Recurrent pneumonia, hemoptysis, and chest pain are also common.
Paraneoplastic syndromes, including Cushing syndrome due to ectopic ACTH, acromegaly due to ectopic growth hormone–releasing factor, and Zollinger-Ellison syndrome due to ectopic gastrin production, are more common than carcinoid syndrome, which occurs in < 3% of patients with the tumor.
Carcinoid syndrome symptoms include
Chronic sequelae of carcinoid syndrome include
A left-sided heart murmur (mitral stenosis or regurgitation) due to serotonin-induced valvular damage occurs rarely with bronchial carcinoids (as opposed to the right-sided valvular lesions of GI carcinoid).
Diagnosis of bronchial carcinoid is based on bronchoscopic biopsy, but evaluation often initially involves chest CT, which reveals tumor calcifications in up to one third of patients.
Indium-111–labeled octreotide scans are useful for determining regional and metastatic spread.
Increased urinary serotonin and 5-hydroxyindoleacetic acid levels support the diagnosis, but these substances are not commonly elevated.