Lung carcinoid tumors are malignant tumors composed chiefly of neuroendocrine cells. The lungs, like the rest of the body, contain these cells. Because they both generate hormones or hormone-like compounds, they are comparable to endocrine cells. They are similar to nerve cells since both may release neurotransmitters. Neuroendocrine cells may sometimes develop too fast and create a tiny tumor called a carcinoid tumor. Besides, lung carcinoid tumors can develop in every organ in the body, not only the lungs.