Bronchial carcinoid tumors are carcinoid tumors primarily occurring in relation to a bronchus. They were previously incorrectly termed bronchial adenomas. They usually occur in association with a segmental or larger bronchus.
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Epidemiology
Typically affects patients from the 3rd to 7th decades with the mean age around 45 years 7,10.
Associations
Cushing syndrome: due to ACTH-producing carcinoid tumor types 1
Clinical presentation
The presentation can vary depending on location. Central neoplasms can cause bronchial obstruction and distal pneumonia, atelectasis, bronchiectasis, air-trapping or lung abscess. Partial airway obstruction can cause cough, wheezing and recurrent pulmonary infections. Peripheral tumors are generally asymptomatic and can cause air-trapping. Presentation with carcinoid syndrome is rare (~2-5%) 5,10.
Pathology
They are neuroendocrine neoplasms that range from low-grade typical carcinoids to more aggressive atypical carcinoids.
Location
Most (~60%) occur centrally within the major bronchi, or rarely within the trachea 4.
Radiographic features
Plain radiograph
Tumors may be seen as filling defects in the main bronchi or trachea with sharp, possibly notched margins 2. Associated airway stenosis with pulmonary atelectasis may be also seen.
CT
Central lesions are usually seen as:
a single hilar or perihilar mass that is usually well-defined, round or ovoid
can be of any size but are typically 2-5 cm
there is often marked homogeneous contrast enhancement due to high vascularity
calcification (usually eccentric) can occur but is not a common feature
Nuclear medicine
PET-CT
F18-FDG PET-CT helps to distinguish aggressive tumors: well-differentiated carcinoid tumors ususally show low FDG avidity. FDG avidity is increased in high-grade and poorly differentiated carcinoid tumors 14.
Gallium-68 DOTATATE
Gallium-68 DOTATATE has shown high accuracy, better imaging quality and lower radiation dose than octreotide scan. Its sensitivity and specificity reaches 80% to 95% as it contains a synthetic somatostatin analog that has high affinity for somatostatin 2 receptors on the surface membrane of well-differentiated primary and metastatic neuroendocrine tumors 14.
