Monday, June 29, 2009

Intestinal Carcinoid

CT Enteroclysis of 55 year old male came with history of dull aching intermittent pain abdomen with episodes of subacute intestinal obstruction. The axial contrast enhanced CT enteroclysis image shows a well defined brilliantly enhancing focal lesion seen in the right iliac fossa causing significatn luminal narrowing of one of the ileal loop. Rest of the structures of abdomen were unremarkable. The coronal refoamatted image better shows the relation with the iliac vessels.

Histology: Carcinoid tumors are relatively rare neuroendocrine tumors. They constitute approximately 2% of all gastrointestinal tumors. Carcinoid tumors belong to a category of tumors called apudomas (amine precursor uptake and decarboxylation tumors) because they arise from endocrine amine precursor uptake and decarboxylation cells that can be found throughout the gastrointestinal tract and in other organs such as the pancreas and the lung. Microscopically, carcinoid tumors are made up of small round regular cells containing a round nucleus and clear cytoplasm. A prominent nucleolus is often present. he presence of elevated excretion of 5-hydroxyindoleacetic acid (5-HIAA) is suggestive of a functioning carcinoid tumor.
Clinical Presentation : Carcinoid tumors are characteristically slowly growing tumors that may go unrecognized for many years. The symptoms are often vague, such as intermittent abdominal pain. The diagnosis is typically not made until the patient undergoes exploratory surgery. These tumors most commonly occur in the fifth or sixth decade of life. The average time from the onset of symptoms to the diagnosis exceeds 9 years. In many cases the diagnosis is not suspected until the patient develops carcinoid syndrome, which typically does not occur until the disease has spread to the liver. However, only 10% of patients will develop the carcinoid syndrome, which is more common with tumors of the ileum and jejunum but also occurs with bronchial and other carcinoid tumors.
Radiology: Small-bowel carcinoid tumors are neuroendocrine neoplasms that present unique imaging challenges. In their early stages, the tumors are small and confined to the bowel wall. Small-bowel series and enteroclysis may be more sensitive for detection than CT or MRI. As the tumor grows, extension outside the involved bowel loop may occur, with infiltration of the mesentery and desmoplastic reaction, which results in a characteristic appearance on small-bowel contrast examinations and cross-sectional imaging. In patients in whom there is a high clinical suspicion of carcinoid tumor but inconclusive barium studies or CT, angiography can be performed and may show the submucosal mass because of its vascularity.Alternatively, in this situation, CT angiography may also be used to localize the mass on the basis of its vascularity and in many cases may obviate conventional angiography.
In addition to contrast studies and CT, nuclear medicine techniques using indium-111– or iodine-123–labeled octreotide or iodine-131–labeled metaiodobenzylguanidine (MIBG) are helpful for diagnosing and locating carcinoid tumors and identifying their metastases.
Surgery is the mainstay of treatment.

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