Bronchial carcinoid tumours are carcinoid tumours 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.

Epidemiology

Typically affects patients from the 3^rd to 7^th decades with the mean age around 45 years ^7,10.

Associations

• multiple endocrine neoplasia type 1 ¹³

• Cushing syndrome: due to ACTH-producing carcinoid tumour 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 tumours 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

Tumours 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 tumours: well-differentiated carcinoid tumours ususally show low FDG avidity. FDG avidity is increased in high-grade and poorly differentiated carcinoid tumours 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 analogue that has high affinity for somatostatin 2 receptors on the surface membrane of well-differentiated primary and metastatic neuroendocrine tumours ¹⁴.