Pancreatic acinar cell carcinoma with a ductal adenocarcinoma component: a case report and analysis of the histogenesis of the tumor

BACKGROUND: Pancreatic cancer composed of acinar cell carcinoma (ACC) and ductal adenocarcinoma (DAC) is rare, and the clinicopathological characteristics of ACC with DAC have yet to be elucidated. Herein, we report a case of ACC with a DAC component of the pancreas and examined the histogenesis of this tumor. CASE PRESENTATION: A 69-year-old man was admitted to our hospital complaining of appetite loss, constipation, epigastric dull pain, and jaundice. Abdominal computed tomography and magnetic resonance cholangiopancreatography revealed a pancreatic head tumor with dilatation of the bile duct and the distal main pancreatic duct. Under the diagnosis of pancreatic head cancer, a pancreatoduodenectomy was performed. The histology of the resected tumor consisted of mainly ACC with a focus of DAC, which was confirmed by mucin staining and immunohistochemistry for antigens such as BCL10, trypsin, Smad4, p16, p53, and MUC1. There was histological transition between the components of ACC and DAC, and immunostaining of the transitional zone showed equivocal results for the antigens. KRAS was wild-type in both ACC and DAC. The patient was treated with adjuvant chemotherapy with S-1 for 1 year. No evidence of recurrence or metastasis was observed after 9 years of follow-up. CONCLUSIONS: A rare case of pancreatic ACC with a DAC component in a patient with long-term survival after surgery was reported. Immunohistochemical and molecular analysis indicated that DAC might have arisen from ACC through transdifferentiation in this case.