The term bronchial adenoma describes a diverse group of tumors arising from mucous glands and ducts of the trachea (windpipe) or bronchi (large airways of the lung). This term describes all of the following types of tumors: neuroendocrine tumors (carcinoids), adenoid cystic carcinomas (cylindromas), mucoepidermoid carcinomas, mucous gland adenomas, and other mixed seromucinous tumors arising from mucous glands and ducts of the windpipe and large airways.

 These tumors are of widely variable malignant (cancerous) potential, although most of them are low-grade malignancies, growing and spreading much more slowly than true lung cancer. Only mucous gland adenomas are truly benign (noncancerous), lacking even the potential to turn malignant.