Carcinoid tumors

Carcinoid tumors are a type of neuroendocrine tumor that can occur in a number of locations. Carcinoid tumors arise from endocrine amine precursor uptake and decarboxylation (APUD) cells that can be found throughout the gastrointestinal tract as well as other organs (e.g. lung). In general, they are slow-growing tumors but are nevertheless capable of metastasizing.

Clinical presentation

  • can be variable, dependent on the location:
    • carcinoid tumors involving the jejunum and ileum can be large at presentation but are usually found incidentally
    • rectal carcinoids may cause pain
    • gastrointestinal tract carcinoid can present as vague abdominal pain
  • carcinoid syndrome: in 8% of patients with a carcinoid tumor

Pathology

Location
Markers
  • 5-HIAA (5-hydroxyindoleacetic acid): usually suggests a functioning carcinoid tumor
  • chromogranin A (CgA): considered a valuable tool in the diagnosis of neuroendocrine neoplasia in general

Radiographic features

CT/MRI

Refer to specific articles (above) for imaging characteristics.

Nuclear medicine
  • gallium-68 octreotide PET/CT (e.g. Ga-68 DOTATATE) has shown improved accuracy for detection of neuroendocrine tumors relative to indium-111 pentetreotide (Octreoscan) SPECT/CT 
  • indium-111 octreotide (e.g. Octreoscan) SPECT/CT
  • iodine-123 MIBG will also concentrate on carcinoid tumors, including the low percentage (~15%) that are negative with indium-111 octreotide

Treatment and prognosis

Complications

History and etymology

It was initially coined by Oberndorfer in 1907 as “karzinoide” to denote its resemblance to carcinoma .