Immunohistochemical expression of SMAD4, CK19, and CA19-9 in fine needle aspiration samples of pancreatic adenocarcinoma: Utility and potential role

BACKGROUND: Pancreatic adenocarcinoma comprises 85% of all cases of pancreatic malignancies. From a diagnostic standpoint, these tumors are readily diagnosed by fine needle aspiration, with an accuracy of greater than 90%; however it is often difficult to ascertain whether these are primary or metastatic in nature. This study was undertaken to see the usefulness of CK19, CA19-9 and a newly described marker, SMAD4 in confirming the pancreatic origin of these tumors. Briefly, SMAD4 (DPC4) is a tumor-suppressor gene located on chromosome 18q which has been shown to mediate the downstream effects of TGF-β superfamily signaling, resulting in growth inhibition. The loss of SMAD4, which as been reported to occur in 55% of pancreatic ductal adenocarcinomas may lead to up regulation of cell cycle proteins and hence increase cellular proliferation. In addition, SMAD4 has been suggested to possibly have prognostic potential, with the presence of SMAD4, indicating shorter survival after resection. DESIGN: Clinical data was reviewed to identify patients with proven, primary pancreatic adenocarcinoma. A total of 25 patients with diagnostic material from fine needle aspiration cell blocks, were retrieved from our files at Emory University Hospital. In addition cell blocks from clinically diagnosed non-pancreatic adenocarcinomas were also selected as controls for this study (10 cases of colonic adenocarcinoma, 10 cases of pulmonary adenocarcinoma, 10 cases of breast ductal carcinoma and 10 cases of ovarian mucinous adenocarcinoma). Formalin fixed, paraffin-embedded sections from these were stained with SMAD4, CK19, and CA19-9, using pressure cooker antigen retrieval, labeled polymer HRP (DAKO), and the DAKO autostainer. RESULTS: Immunohistochemical staining was reviewed based on intensity (negative, low-positive, and high-positive) and percentage of cells. In primary pancreatic ductal adenocarcinoma, CK 19 showed diffuse cytoplasmic positivity in 23 of 25 cases, CA 19-9 showed apical cytoplasmic staining in all 25 cases, and SMAD4 showed nuclear staining in 20 of 25 cases. In the control group comprising of non-pancreatic adenocarcinoma SMAD4 was negative (100%) in all 10 cases of colonic and pulmonary adenocarcinoma. However 1 of 10 cases (10%) of breast and ovarian adenocarcinoma did show low positivity nuclear staining. However the expression of CA19-9 and CK19 was more variable in these different non-pancreatic malignancies. CONCLUSION: Pancreatic adenocarcinoma showed positive immunohistochemical staining for SMAD4 in 80%, CK19 in 100% and CA19-9 in 100% of the selected cases. These markers, when used as a panel, may confirm the diagnosis of pancreatic adenocarcinoma in fine needle aspiration samples, and help in differentiating from metastatic adenocarcinoma. This may help in determination of appropriate surgical and chemotherapeutic options.