Proliferation tissue polypeptide antigen distinguishes malignant mucinous cystadenocarcinomas from benign cystic tumors and pseudocysts

Background Cystic lesions of the pancreas include inflammatory pseudocysts, serous cystadenomas, and mucinous cystic tumors, some of which are malignant. Previous studies have shown that malignant mucinous tumors differ from benign pancreatic cysts in proliferative activity, secretion of tumor markers, and expression of growth factor receptors. Analysis of aspirated cyst fluid for tumor markers, viscosity, and cytologic examination has been proposed as an aid to preoperative differential diagnosis. Tissue polypeptide antigen (TPA) is a soluble proliferation antigen produced by rapidly dividing tissues, including conventional ductal pancreatic carcinoma. TPA levels in pancreatic cyst fluids have not been reported. Methods Tissue polypeptide antigen levels were determined in 46 pancreatic cyst fluids using a commercial immunoassay technique. Results Mucinous cystadenocarcinomas exhibited significantly higher levels of cyst fluid TPA than benign cystic lesions, including pseudocysts, serous cystadenomas, and benign mucinous cystadenomas (mean 910,672 U/mL, median 300,900 U/mL, range 16,600 to 4,210,000 U/mL for malignant mucinous Cystadenocarcinomas; versus mean 16,082 U/mL, median 2,455 U/mL, range 0 to 155,000 U/mL for benign cystic lesions considered as a group; P<0.0002). In 75% of the malignant cysts, the TPA values were in excess of 100,000 U/mL. Pseudocysts exhibited the lowest TPA levels (mean 2,108 U/mL, median 604 U/mL, range 0 to 20,240 U/mL) and were slgniflcantly lower than the values observed in cystic tumors (P<0.0005). Serous and benign mucinous tumors had intermediate levels of TPA. Conclusions Elevated levels of the proliferation antigen TPA in malignant pancreatic cysts correlate with earlier observations of increased proliferative activity and overexpression of growth factor receptors in these tumors. The TPA measurement may be a useful addition to previously reported cyst fluid markers to aid in preoperative differential diagnosis. Markedly elevated or very low values indicate a malignant or benign cyst, respectively.