A case of pancreatic ductal adenocarcinoma with marked infiltration with IgG4-positive cells
A 75-year-old man without a history of malignancy was referred to our institution because of weight loss and a mass lesion in the pancreas tail. The laboratory studies were unremarkable. The patient's CEA level was elevated (12.7 ng/mL; normal, 0-6 ng/mL), but the CA 19-9 level was within the normal range (25.6 U/mL; normal, 0-37.0 U/mL). No increase was noted in the serum amylase level (51 IU/L; normal value, 25-120 IU/L) or the lipase level (22 U/L; normal value, 13-49 U/L). Dynamic-enhanced computed tomography (CT) imaging showed a mass measuring 20 mm in the tail of the pancreas with no dilation of the main pancreatic duct, anomalous arrangement of the pancreaticobiliary ducts, or obstructive jaundice. Endoscopic retrograde cholangiopancreatography (ERCP) revealed a narrowing of the main pancreatic duct at the tail. A cytology analysis of the pancreatic juice was negative for tumor cells. These results suggested that the mass lesion in the pancreas was caused by chronic pancreatitis or autoimmune pancreatitis, rather than a pancreatic carcinoma. Further laboratory tests showed a normal IgG level (1100 mg/mL; normal, 800-1800 mg/mL), a normal IgG4 level (67.0 mg/mL; normal, 4-180 mg/mL) and the absence of antinuclear antibody. The EUS-FNA specimens showed a mixture of abnormal columnar epithelia and abundant lymphocytes. A diagnosis of pancreas cancer was made, and a pancreatosplenectomy was performed.\nSmear preparations of the EUS-FNA materials from the pancreas tumor were stained using Diff-Quik solution. Cytoblocks were made by allowing the aspirated materials to clot in 10% buffered formalin, followed by treatment in alginic acid. The smear preparations showed numerous lymphocytes including plasma cells with necrotic material [] and small clusters of atypical epithelial cells []. The atypical cells had a high nuclear to cytoplasmic ratio; the cells were hyperchromatic and contained prominent nucleoli. The Papanicolaou-stained smear preparations and the cytoblock preparations showed similar findings. In the cytoblock specimens, some plasma cells were immunoreactive to anti-IgG4 antibody.\nThe cut surface of the resected pancreas showed an elastic, hard, white mass in the pancreas tail []. In the histopathologic examination, intralobular and interlobular fibrosis was observed, with numerous lymphocyte and plasma cell infiltrations. No granulocytic epithelial lesions were found, so these histological features were compatible with the characteristics of type 1 autoimmune pancreatitis-lymphoplasmacytic sclerosing pancreatitis (Type 1 AIP-LPSP). Invasive ductal adenocarcinoma with lymphoplasmacytic infiltration was also observed in these lesions []. Immunohistochemical staining, revealed abundant IgG4-positive plasma cells (>50 cells per high-power field [HPF]) around the pancreatic duct and tumor cells []. The pathological diagnosis was moderately differentiated tubular adenocarcinoma with abundant lymphoplasmacytic infiltration and AIP-LPSP features.