Expression profile of mucins in ovarian mucinous tumors: distinguishing primary ovarian from metastatic tumors.

Ovarian mucinous tumors (OMTs) of the intestinal type share morphologic features with primary tumors of other sites, and it can often be difficult to distinguish primary ovarian from metastatic mucinous tumors. MUC1, MUC2, MUC5AC, and MUC6 expressions were studied by immunohistochemistry in 36 OMTs of intestinal type (17 malignant, 19 borderline), 18 pancreatic, 12 biliary, 15 esophageal, 9 gastric, and 7 colorectal/appendiceal adenocarcinomas. All samples were from primary sites, except for colorectal tumors which were from ovarian metastases. Borderline and malignant OMTs show similar mucin immunoprofile, being strongly and uniformly positive for MUC5AC (97.2% of cases), whereas only focally positive for MUC1 (19.4%), MUC2 (38.9%), and MUC6 (22.2%). The positive frequencies of pancreatic adenocarcinomas for MUC1, MUC2, MUC5AC, and MUC6, respectively, were 100%, 16.7%, 94.4%, and 61.1%; for biliary (cholangiocarcinomas) were 91.7%, 0%, 16.7%, and 8.3%; for esophageal carcinomas were 73.3%, 33.3%, 53.3%, and 26.7%; for gastric carcinomas were 44.4%, 44.4%, 44.4%, and 0% and for lower gastrointestinal tract cancers were 28.6%, 85.7%, 42.9%, and 0%. Our study shows that OMTs are usually MUC5AC+/MUC1-, which is different from pancreatic, biliary, esophageal, gastric, and colorectal/appendiceal carcinomas. We recommend that these mucin stains be added to the panel of immunostains to differentiate metastatic tumors to the ovary from primary OMTs.