...inoid lung tumor? - What is a Carcinoid Lung Tumor?There are a few types of tumors that can neither be classified as benign (noncancerous) or malignant (cancerous). Their clinical behavior falls between the two classifications of benign and malignant, and they have sometimes been called "midway" tumors. They were so named in an attempt to designate these tumors as midway between cancers and benign tumors. Among these rare tumors are carcinoid tumors.Carcinoid tumors have also been called "cancers in slow motion." Even though they have the potential for being malignant, they mostly tend to grow so slowly that people with carcinoid tumors usually live for many years (sometimes for a normal lifetime).Carcinoid lung tumors are an uncommon group of lung tumors, developing from neuroendocrine cells. The neuroendocrine cells are in some respect like nerve cells and in other ways like cells of endocrine (hormone-producing) glands. These cells are scattered throughout the body and can be found in different organs, for instance, the lungs, stomach, and intestines. These neuroendocrine cells can form growths (tumors) in many different organs, but usually occur in other endocrine glands such as the adrenal or thyroid glands, or the intestinal tract.The uncontrolled growth of neuroendocrine cells leads to the development of carcinoid tumors. Most carcinoid tumors originate in the small intestine, but carcinoid lung tumors represent about 10% of all carcinoid tumors. Carcinoid lung tumors comprise 1%-6% of all lung tumors.There are two types of carcinoid lung tumors: typical and atypical.Typical carcinoid lung tumors are about nine times more common than atypical carcinoid lung tumors. These tumors characteristically grow slowly and only rarely metastasize (spread) beyond the lungs.Atypical carcinoid lung tumors are more aggressive than typical carcinoid lung tumors and are somewhat more likely to metastasize to other organs. They comprise about 10% of all carcinoid lung tumors.Some carcinoid tumors produce hormone-like substances that can cause a number of endocrine syndromes. The term carcinoid syndrome has been used to refer to the collection of symptoms produced when a carcinoid tumor secretes hormone-like substances. These syndromes tend to reflect the excessive response of the body to the hormone-like substances produced. However, carcinoid syndrome occurs in only about 2% of people with carcinoid lung tumors.About 25% of lung carcinoid tumors are located within the airways and are referred to as bronchial carcinoids. These are not related to smoking or other environmental causes. While anyone can develop a carcinoid tumor of the lung, they may be slightly more common in African-American males.