OBJECTIVETo study the pathologic features, diagnosis, differential diagnosis and molecular characteristics of colloid carcinoma of the pancreas.

METHODSThe clinical findings, morphologic features, immunophenotype and K-ras gene alterations were investigated in 4 cases of pancreatic colloid carcinoma.

RESULTSIn the 4 cases of colloid carcinoma of the pancreas, three tumors were located in the head of the pancreas, one was located in the body and tail. The average age was 56.5 years old. The presenting symptom was abdominal pain in 2 cases, increased level of U-GLU in 1 patient, and an accidental finding presented in 1 patient. Grossly, 3 cases were cystic and solid, with mucin in the cyst; 1 case was solid. Microscopically, the colloid carcinoma was characterized by large pools of extracellular mucin, containing neoplastic cells, which were in the pattern of cuboidal, cribriform or irregular clusters, or formed an incomplete lining separating mucin pools from the stroma. Three cases developed from pre-existing pancreatic ductal adenocarcinoma (IPMN), intestinal-type, and 1 from IPMN, pancreatobiliary-type. Immunohistochemical studies showed that MUC2 was positive in 3 cases, and MUC1 in 1 case. K-ras gene mutation was identified in 2 cases, showing a single-amino-acid substitution in codon 12, as Gly12Asp (GGT > GAT) and Gly12Arg (GGT > CGT).

CONCLUSIONSPancreatic colloid carcinoma is a rare variant of pancreatic ductal adenocarcinoma, which is associated with IPMN and mucinous cystic neoplasms. Positive MUC2 staining and absent MUC1 expression are commonly found, and K-ras gene mutation is occasionally identified in these tumors.