Uncommon presentations of common pancreatic neoplasms: a pictorial essay

Abstract

Pancreatic neoplasms are a wide group of solid and cystic lesions with different and often characteristic imaging features, clinical presentations, and management. Among solid tumors, ductal adenocarcinoma is the most common: it arises from exocrine pancreas, comprises about 90% of all pancreatic neoplasms, and generally has a bad prognosis; its therapeutic management must be multidisciplinary, involving surgeons, oncologists, gastroenterologists, radiologists, and radiotherapists. The second most common solid pancreatic neoplasms are neuroendocrine tumors: they can be divided into functioning or non-functioning and present different degrees of malignancy. Cystic pancreatic neoplasms comprise serous neoplasms, which are almost always benign, mucinous cystic neoplasms and intraductal papillary mucinous neoplasms, which can vary from benign to frankly malignant lesions, and solid pseudopapillary tumors. Other pancreatic neoplasms, such as lymphoma, metastases, or pancreatoblastoma, are rarely seen in clinical practice and have different and sometimes controversial managements. Rare clinical presentations and imaging appearance of the most common pancreatic neoplasms, both solid and cystic, are more frequently seen and clinically relevant than rare pancreatic tumors; their pathologic and radiologic appearances must be known to improve their management. The purpose of this paper is to present some rare or uncommon clinical and radiological presentations of common pancreatic neoplasms providing examples of multi-modality imaging approach with pathologic correlations, thus describing the histopathological bases that can explain the peculiar imaging features, in order to avoid relevant misdiagnosis and to improve lesion management.

Morphological differentiation and follow-up of pancreatic cystic neoplasms using endoscopic ultrasound

“…Solid pseudopapillary tumors,[ 39 40 ] cystic neuroendocrine neoplasms of the pancreas,[ 41 42 43 44 ] acinar cell neoplasms,[ 45 ] and pancreatic adenocarcinomas (adenosquamous and/or anaplastic carcinoma)[ 46 ] can occasionally appear as cystic masses.…”

Imaging presentation of pancreatic neuroendocrine neoplasms

“…DWI may help in the detection of P-NENS, especially for localizing non-hypervascular neoplasms [ 21 ]. It has been reported that P-NENs with different grades of differentiation can be distinguished evaluating ADC maps: poor-differentiated P-NENs have significantly lower mean ADC values compared to normal pancreatic tissue and to well-differentiated pancreatic neuroendocrine tumors [ 22 – 24 ]. DWI MR could predict pancreatic neuroendocrine tumor grade, as reported in the literature, playing a role in tumor prognostic stratification at the beginning of the clinical history of the patient [ 25 ].…”

“…P-NENs could show atypical behavior. The most common atypical presentations are the hypoenhancing pattern, the intravessels growth, the intraductal growth, and the cystic and calcified variants [ 22 ].…”

“…Actually, hypovascular P-NENs are not so rare, reaching 49% in a group of patients with NENs in the clinical records of Jeon et al [ 27 ]. This appearance is directly related to the amount of dense and hyalinized stroma within the tumor, and to the small lesion dimension or of its vascular network [ 22 , 28 , 29 ]. It is crucial to carefully evaluate all the other imaging characteristics (size, margins, growing pattern, and main pancreatic duct aspect) in order to carry out an accurate differential diagnosis and to differentiate them from ductal adenocarcinoma, because these two entities may have a completely different management and, last but not least, a completely different prognosis [ 22 ].…”

Radiological Workup of Cystic Neoplasms of the Pancreas

“…Uncommon presentations of IPMNs include the dilatation of the entire ductal system (pan-ductal-ectasia), invasion or fistulation of adjacent structures such as bowel loops or common bile duct, and rarely intra-abdominal perforation resulting in pseudomyxoma peritonei [43]. …”