Document Type : Case Report
Research Institute for Nuclear Medicine, Tehran University of Medical Sciences, Tehran, Iran
A 65 years old male presented with abdominal pain (R.U.Q) and constipation, associated with weight loss and anorexia since 40 days prior to admission. Serum biochemical tests were normal. Colonoscopy showed hemorrhagic polypoid lesion in the cecum. Barium enema revealed filling defect in the cecum. Sonography revealed a target-shaped lesion (3cm×2.5cm) in upper segment of the right hepatic lobe. CT scan confirmed the same finding as a hypodense lesion. Following segmental resection of the cecum, pathology indicated the presence of the carcinoid tumor. For better evaluation, ¹³¹I-MIBG scintigraphy was carried out, demonstrating tracer avid metastatic lesions in the right and left hepatic lobes. A review of the series reported in the literature shows that approximately 50-60% of carcinoids are able to concentrate radiolabeled MIBG. MIBG uptake apparently correlated with the urinary excretion of 5-HIAA, although this is not a universal finding. The most frequently occurring midgut carcinoids probably concentrate radiolabeled MIBG more readily than those in the hindgut and foregut. Primary and residual tumors are sometimes visualized, but the most striking imaging is that of carcinoid metastases in the peritoneum and liver (Provided that SPECT images with ¹²³I-MIBG or alternatively ¹³¹I-MIBG delayed scans are performed). Lymph node involvement, bone deposits and ovarian metastases have been reported as well. When radioiodinated MIBG and somatostatin scintigraphy results are compared, somatostatin scintigraphy shows a better sensitivity (>80%) in detecting both primary and metastatic lesions. These radiopharmaceuticals play complementary roles in that each give unique information concerning possible treatment either with octreotide or ¹³¹I-MIBG, or both. MIBG imaging cannot generally be relied upon either to detect a carcinoid, or to rule out the disease. When a tumor is strongly suspected of being a carcinoid however, the test can be worthwhile for the following reasons: 1) To disclose any residual/recurrent tumor, in the event that it is not shown by other techniques. 2) To better define the staging. 3) As a prelude to 131-MIBG therapy.