A cystadenoma is a type of benign tumor that typically forms in the ovaries or pancreas. It is characterized by the presence of cysts, which are fluid-filled sacs. These tumors are generally non-cancerous and can vary in size. While they may not cause symptoms, larger cystadenomas can lead to discomfort or complications. Cystadenomas are classified into two main types: serous and mucinous. Serous cystadenomas are usually filled with a thin, watery fluid, while mucinous cystadenomas contain a thicker, gel-like substance. Diagnosis often involves imaging techniques like ultrasound or CT scans, and treatment may include monitoring or surgical removal if necessary.