PROLIFERATION TISSUE POLYPEPTIDE ANTIGEN DISTINGUISHES MALIGNANT MUCINOUS CYSTADENOCARCINOMAS FROM BENIGN CYSTIC TUMORS AND PSEUDOCYSTS

BACKGROUND: Cystic lesions of the pancreas include inflammatory pseudo cysts, serous cystadenomas, and mucinous cystic tumors, some of which are malignant. Previous studies have shown that malignant mucinous tum ors differ from benign pancreatic cysts in proliferative activity, sec retion of tumor markers, and expression of growth factor receptors. An alysis of aspirated cyst fluid for tumor markers, viscosity, and cytol ogic examination has been proposed as an aid to preoperative different ial diagnosis. Tissue polypeptide antigen (TPA) is a soluble prolifera tion antigen produced by rapidly dividing tissues, including conventio nal ductal pancreatic carcinoma. TPA levels in pancreatic cyst fluids have not been reported. METHODS: Tissue polypeptide antigen levels wer e determined in 46 pancreatic cyst fluids using a commercial immunoass ay technique. RESULTS: Mucinous cystadenocarcinomas exhibited signific antly higher levels of cyst fluid TPA than benign cystic lesions, incl uding pseudocysts, serous cystadenomas, and benign mucinous cystadenom as (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 lesio ns considered as a group; P<0.0002). In 75% of the malignant cysts, th e 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 20,24 0 U/mL) and were significantly lower than the values observed in cysti c tumors (P<0.0005). Serous and benign mucinous tumors had intermediat e levels of TPA. CONCLUSIONS: Elevated levels of the proliferation ant igen TPA in malignant pancreatic cysts correlate with earlier observat ions 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 preoperat ive differential diagnosis. Markedly elevated or very low values indic ate a malignant or benign cyst, respectively.