Peripheral pulmonary carcinoid tumor
Peripheral pulmonary carcinoid tumor refers to a subtype of pulmonary carcinoid tumors that arise within the periphery of the lung. They are considered less common than the more centrally-located bronchial carcinoid tumors.
Clinical presentation
Many patients tend to be asymptomatic . Presentation with carcinoid syndrome is extremely rare .
Pathology
Peripheral pulmonary carcinoid tumors are considered a neuroendocrine tumor of the lung. They can be
- typical pulmonary carcinoid tumors (well-differentiated - common) or
- atypical pulmonary carcinoid tumors (more aggressive - uncommon)
Risk factors
- smoking: the rate of carcinoid tumors is similar between smokers and non-smokers, although there is an increased incidence of atypical subtype amongst smokers
Radiographic features
CT
Most are discovered as an incidental rounded solitary pulmonary nodule. The size at diagnosis can vary but is usually reported to be in the range of 10-30 mm . Many have a lobulated margin with an average Hounsfield value on postcontrast imaging of ~50 . Imaging features are often non-specific and tissue diagnosis is essential in determining diagnosis.
Most peripheral carcinoid tumors tend to involve a subsegmental bronchus .
Nuclear medicine
FDG-PET
May have a sensitivity of around 75%. Although most cases will show uptake on an 18-FDG PET, up to a quarter of false-negative has been described .
Gallium68-Octreotide-PET / Ga-DOTATATE
Usually avid and useful for diagnosis .
Treatment and prognosis
Some authors consider there as complex tumors as a whole which require a multidisciplinary approach and long-term follow-up .
Differential diagnosis
See differentials for a solitary pulmonary nodule.
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