Cyst fluid tumor-associated trypsin inhibitor may be helpful in the differentiation of cystic pancreatic lesions.

In clinical practice it is important to differentiate pseudocysts from cystic pancreatic tumors, especially potentially malignant mucinous cystic tumors. We investigated three new markers-tumor-associated trypsin inhibitor (TATI) and the free alpha and beta subunits of human choriogonadotropin (hCGalpha and hCGbeta, respectively)-in the cyst fluid of patients with cystic pancreatic lesions and compared the concentrations of these markers to those of carcinoembryonic antigen (CEA), CA 19-9, CA 242, CA 125, CA 15-3, alpha-fetoprotein, and tissue polypeptide antigen in order to distinguish benign cysts from malignant cysts. Between 1995 and 2001, a total of 34 patients operated on for cystic pancreatic lesions at Tampere University Hospital were included. Cyst fluid was aspirated at operation and stored at -70 C. The histologic diagnosis was pseudocyst in 23 patients, serous cystadenoma (SCA) in four patients, benign mucinous cystadenoma (MCA) in four patients, cystic papillary neoplasm (CPN) in one patient, glucagonoma in one patient, and malignant endocrine islet cell carcinoma (EC) in one patient. Significantly higher concentrations of TATI were found in patients with MCA and EC (2239 +/- 149 microg/L [mean +/- SEM]) than in patients with pseudocyst (55 +/- 29 microg/L; P=0.001) and in patients with SCA (36 +/- 23 microg/L; P=0.01). The patient with CPN and the patient with glucagonoma had relatively low levels of TATI (30.7 and 46.5 microg/L). Mean CEA was higher in patients with MCA compared to those with pseudocysts (19,993 +/- 9418 vs. 53 +/- 20 microg/L, P=0.002) and SCA (0.4 +/- 0.1 microg/L; P=0.02), but in the patient with malignant EC, the patient with CPN, and the patient with glucagonoma, CEA was normal. HCGalpha, hCGbeta, CA 19-9, CA 242, CA 125, CA 15-3, alpha fetoprotein, and tissue polypeptide antigen could not distinguish between MCA vs. pseudocyst or SCA, because both normal and elevated values were seen in all groups. To our knowledge, this is the first time that TATI has been quantitated in the cyst fluid of patients with cystic pancreatic lesions. It appears to be a potential marker in the differential diagnosis of benign from malignant cystic pancreatic lesions.