Mucinous cystadenoma is a benign cystic tumor lined by a mucinous epithelium. It is a type of cystic adenoma (cystadenoma). Mucinous cystadenomata may arise in a number of locations; however, mucinous cystadenoma at different locations are not generally considered to be related to one another. Overview Mucinous cystadenomas may be found in the: Ovary—ovarian mucinous cystadenoma Pancreas—pancreatic mucinous cystadenoma Peritoneum—peritoneal mucinous cystadenoma Liver—mucinous cystadenoma of the liver Vermiform appendix—appendiceal mucinous cystadenoma (see cystadenoma) Ovarian mucinous cystadenoma Mucinous cystadenomas make up 15–20% of all ovarian tumors. They often become very large and can extend up into the abdomen. These tumors are usually evaluated using ultrasound, CT scan, or MRI. Findings on imaging studies are nonspecific. These ovarian tumors are usually multi-septated, cystic masses with thin walls. They also contain varying amounts of solid tissue which consists of proliferating stromal tissue, papillae, or malignant tumor cells. Benign mucinous cystadenomas compose 80% of mucinous ovarian tumors and 20–25% of benign ovarian tumors overall. The peak incidence occurs between 30 and 50 years of age. Benign tumors are bilateral in 5–10% of cases. Macroscopy Microscopy Types Pancreatic Pancreatic mucinous cystadenoma or mucinous cystadenoma of the pancreas (MCN) are a type of mucinous cystic neoplasm of the pancreas. The cure rate is very high in cases on benign cystic lesions, but the case changes if malignant changes ensue. Benign cystadenomas are the most common cystic tumors of the pancreas accounting for 75% of the cases. On an average, mucinous accounts for 40–50% of cystic tumors, and serous cytadenoma accounts for 30% of it. Mucinous cystadenomas are in the dital pancreas in about 80% of the cases and distal pancreatectomy is needed for resection. In 20% of the cases it is in the head of the pancreas. Earlier it was believed that MCN occurs exclusively in females who are middle aged. However, occasional occurrence in men have been reported, especially those who are 45 years of age or above. Liver A rare neoplasm, 95% cases occur in women, especially at the mean age of 45. Biliary cystadenoma and cystadenocarcinoma constitute less than 5% of intrahepatic cysts originating from the bile duct. Cystadenomas in liver are often confused with hydatid cyst as their appearance on various imaging techniques is nearly same. Treating cystadenomas as hydatid cyst has resulted in recurrence of the cyst. Primary retroperitoneal Cases of primary retroperitoneal mucinous cystadenoma (PRMC) are extremely rare. However, they