Small undifferentiated pancreatic adenocarcinoma which mimics IPMN at imaging

CONTEXT: To present the case of an unusual presentation at imaging of a very small solid undifferentiated pancreatic adenocarcinoma which mimics a side-branch intraductal papillary mucinous neoplasm. CASE REPORT: The patient came to our hospital for a revaluation of a cystic pancreatic lesion. Ultrasound (US) and contrast-enhanced ultrasound (CEUS) examinations were carried out. A small cystic lesion of about 1.5 cm in diameter was seen in the posterior aspect of the pancreatic uncinate process A very small, solid, vascularized nodule was detected at CEUS within the lesion. Consequently, the patient underwent CT and MRI. MRI confirmed the presence of an intralesional nodule and communication with the main pancreatic duct was demonstrated, suggesting the diagnosis of intraductal papillary mucinous neoplasm with solid intralesional tissue. A pylorus preserving pancreaticoduodenectomy was carried out. An undifferentiated adenocarcinoma having a notable peripheral inflammatory reaction and dilated branch duct was finally diagnosed. CONCLUSION: To our knowledge, we present for the first time, the case of a very small solid undifferentiated pancreatic adenocarcinoma of the uncinate process which mimicked a side-branch intraductal papillary mucinous neoplasm at imaging. The cystic appearance may be an epiphenomenon of a solid lesion and this possibility has to be considered when one encounters incidental cystic lesions at imaging.