A mucinous tumor is a cystic neoplasm filled with mucus-like material called mucin and lined by atypical epithelial cells. It can be a benign mucinous cystadenoma or a malignant mucinous cystadenocarcinoma. Benign mucinous tumors often have several cystic lobes lined by a smooth lining of epithelium. Malignant mucinous tumors often have solid areas and papillae with cellular atypia and stratification, abnormality in tissue architecture, and necrosis. Cells of mucinous tumors resemble endocervical or intestinal cells.
Mucinous cystadenoma accounts for most mucinous tumors and is commonly associated with appendiceal, colonic, ovarian, and pancreatic tumors. In appendiceal and colonic mucinous tumors, benign mucinous cystadenoma has the same gross appearance as malignant mucinous cystadenocarcinoma, and can only be differentiated through histopathological examination. About 15 to 25% of all ovarian neoplasms are ovarian mucinous tumors, and around 6 to 10% of ovarian mucinous tumors are malignant. Mucinous tumors in the pancreas are also quite common.
Benign mucinous ovarian tumors are commonly found in child-bearing aged women, while malignant mucinous ovarian tumors are commonly found in women between 30 and 60 years old. An ovarian mucinous tumor is usually unilateral, and bilateral involvement with a mucinous tumor warrants further examination. About 5% of bilateral ovarian mucinous tumors are benign, while about 10 to 20% of bilateral ovarian mucinous tumors are malignant.
About two-thirds of the instances of mucinous tumor formation are in the tail or body of the pancreas. These are commonly seen in perimenopausal women. They are slow-growing tumors wherein affected individuals usually do not suffer from pain. Pancreatic mucinous cystadenoma account for 45% of pancreatic tumors, and intraductal papillary mucinous adenoma account for 32%. There are also borderline and malignant pancreatic mucinous tumors, but these are less common.
Intraductal papillary mucinous neoplasms are mucin-producing intraductal neoplasms that often involve the head of the pancreas. Medical professionals believe these are commonly found in more men than women, but recent studies point to a trend of equal distribution between the sexes. Affected individuals are usually between 70 and 80 years old and have abdominal pain or recurrent pancreatitis. The lack of tissue invasion distinguishes the benign intraductal papillary mucinous neoplasms from the malignant intraductal papillary mucinous neoplasms. In comparison to mucinous cystic neoplasms, intraductal papillary mucinous neoplasms do not have the dense ovarian stroma and they also involve the pancreatic duct.