I was diagnosed with carcinoid syndrome in march of 2007. i have had yearly ct scans since then, and no tumor has been found. is this common?

Not uncommon: Carcinoid is a type of tumor that usually arises within the gut wall. Though larger tumors can often be seen on ct scans, it is not unusual for a small carcinoid to be difficult to see on ct (especially if it arises in the small bowel). If the carcinoid is aggressive or spreads, ct is likely to see it. A radionuclide test (e.g. Octreoscan) is a useful adjunct when ct does not detect the tumor.