Gastrointestinal carcinoid tumors: a multi-technique diagnostic approach

Carcinoid tumors account for less than 1% of all malignancies. The majority arise in the gastrointestinal system (GI carcinoids). The diagnosis of GI carcinoids is often made late, the protean symptoms are easy to overlook. Diagnosis, prognosis and treatment options are based on biochemical markers and imaging investigations. A high concentration of urinary 5-HIAA or an elevated serotonin level in plasma help to establish the diagnosis of GI carcinoid. Plasma chromogranin A has poor specificity (68%); its level depends on disease involvement and therapeutic response. Octreoscan is the best imaging technique to detect GI carcinoids, but CT scan and MRI are superior for the detection of metastasis. 18F-DOPA or 11C-5-HTP/PET, imaging fusion as of octreoscan or PET scan with CT or MRI, improve the results of metabolic imaging. Coronal contrast-enhanced CT or MRI angiogram can evaluate mesenteric vessel spread before surgery. Upper endoscopy or colonoscopy, can be performed to detect foregut carcinoid in MEN, or hindgut carcinoid. Echoendoscopy visualizes abdominal wall and local node involvement. Enteroscopy and capsule endoscopy localize 66% of midgut carcinoids. Although there have been considerable advances in diagnostic modalities, the diagnosis of carcinoid tumors is still, all too often, late.