Clinical History
A 48 years old man with a previous history of testicular seminoma presented with acute pancreatitis.
Imaging Findings
A 48 years old man with a previous history of orchidectomy for testicular seminoma presented with acute pancreatitis. No known risk factors for acute pancreatitis neither previous episodes of acute pancreatic pain were reported.
Laboratory data showed normal serum levels of amylase, lipase and liver tests. Carcinoembryonic antigen and carbohydrate antigen 19-9 ranges were also normal. An abdominal ultrasound examination depicted liver steatosis, without gallbladder calculi. Abdominal MR and CT were therefore performed.
MR images demonstrated an area of inhomogeneous and slightly T2-hyperintense signal inside the main pancreatic duct (MPD), with MPD upstream dilatation (Fig 1). After gadolinium injection, this intraductal area demonstrated an early and vivid enhancement (Fig 2). Diffusion-weighted (DW) images showed an area of restricted water diffusion superimposed to the pancreatic lesion described (Fig 3). MRCP image showed a filling defect within the MPD with marked dilatation in its caudal portion (Fig 4).
Contrast-enhanced CT images confirmed the presence of intraductal solid tissue with early and sustained enhancement (Fig 5).
Endoscopic ultrasonography-fine needle aspiration cytology (EUS-FNA) was non-conclusive. A total duodeno-pancreatectomy was performed. The resected specimen showed the presence of an intraductal mass with positive immunoreactions for synaptophisin and chromogranin. The final diagnosis was non-functioning pancreatic endocrine tumour T2 (limited to the pancreas and with size of 2-4 cm), N0, grade 2 (Fig 6).
Discussion
Pancreatic endocrine tumours are rare (1-2% of all pancreatic tumours), the non-functioning accounting for roughly 30% [1]. Due to the lack of endocrine symptoms, the latter are generally silent until symptoms related to mass effect manifest; in our case we suggest that the acute pancreatitis could be attributed to an obstruction of the MPD.
A hypervascular mass (with arterial enhancement) is the usual appearance at cross-sectional imaging, whereas intraductal growth of the neoplastic tissue as in the case described is very rare: to our knowledge only four cases have been previously reported in the literature [2].
To explain the intraductal growth of an endocrine tumour the existence of primitive stem cells in the epithelium of the pancreatic duct, which can differentiate to both islet and acinar cells, has been suggested [3].
Main duct type intraductal papillary mucinous tumour (IPMT), solid malignant tumour of exocrine pancreas, metastasis and non-Hodgkin lymphoma were the main differential diagnosis considered. For each a brief discussion is made, with emphasis on pros (featured shared by our case and the differential diagnosis) and contra (features that make this differential unlikely).
MAIN DUCT TYPE IPMT. Pros: intraductal solid tissue in association with upstream dilatation of the MPD and parenchymal atrophy was evident. Contra: no signs of mucin overproduction were visible, which would have led to a cystic ectasia of MPD at the level of the solid tissue [1] (Fig 7).
SOLID MALIGNANT TUMOR OF EXOCRINE PANCREAS. Pros: a mass effect with associated upstream dilatation of the duct and parenchyma atrophy was noted. DW images depicted an area of hyperintense signal, thus indicating restricted water diffusion. Contra: absence of solid tissue component outside the MPD. Presence of a hypervascular lesion: although a few hypervascular acinar cell carcinomas have been described, the classical behaviour of malignant tumours of exocrine pancreas (mainly ductal adenocarcinomas) is hypovascularity [1].
METASTASIS. Pros: the patient had a clinical history of malignancy, and pancreatic metastases from seminoma have been reported. Hypervascularity and even an intraductal growth pattern have been described for renal cell carcinoma metastasis [4]. Contra: the occurrence of solitary, hypervascular pancreatic metastasis is rare.
NON-HODGKIN LYMPHOMA. Pros: although rare, primary pancreatic lymphoma can manifest as a mass. Hyperintense signal in DW images (restricted water diffusion) is also a common finding. Contra: pancreatic lymphoma generally does not produce MPD dilatation and does not exhibit hypervascular enhancement [5].
Differential Diagnosis List
Non-functioning pancreatic endocrine tumor.
Final Diagnosis
Non-functioning pancreatic endocrine tumor.
