Carcinoid Tumors

Carcinoid tumors are a type of slow-growing cancer that usually start in the digestive system or lungs. These tumors arise from special cells called neuroendocrine cells that produce hormones. When the tumor grows, it can release excess hormones into the bloodstream, causing symptoms like flushing, diarrhea, and wheezing, known as carcinoid syndrome. Most carcinoid tumors grow quietly and may not cause symptoms until they spread to other parts of the body. Early detection is important because these tumors can affect how the body regulates important functions like digestion and blood flow.

Carcinoid tumors are well-differentiated neuroendocrine neoplasms arising primarily from enterochromaffin cells in the gastrointestinal tract or bronchopulmonary system. They secrete bioactive amines and peptides, most notably serotonin, which can lead to carcinoid syndrome when tumors metastasize to the liver or beyond. These tumors are characterized by their indolent growth but potential for local invasion and distant metastasis. Histologically, they show uniform cells with salt-and-pepper chromatin and express neuroendocrine markers such as chromogranin A and synaptophysin. The clinical significance lies in their hormone secretion causing systemic symptoms and the risk of fibrosis and cardiac valvular disease. Genetic alterations are less well-defined but may involve pathways regulating neuroendocrine differentiation.