Teaching Case

A 29-year-old woman, with no remarkable medical history, was referred to abdominal ultrasound in the diagnostic work-up for a one-year history of increasing abdominal volume and mild epigastric pain. After sonographic evaluation a CT examination was performed. The routine laboratory profile, including liver function and hormonal testing, was normal.

Ultrasound examination revealed a large heterogeneous mass in the head and uncinate portions of the pancreas, partly cystic with peripheral echogenic solid components.
CT subsequently showed a 10 cm complex mass in the head of the pancreas predominantly cystic, with a thick wall and an eccentric solid component that enhanced after contrast administration. There was a mild dilatation of the duct of Wirsung with no evidence of dilatation of the biliary tree or focal liver lesions.
Trans-gastric fine needle aspiration of the mass showed clear fluid with no neoplastic cells suggesting the diagnosis of pseudocyst.
The patient underwent to surgery for a cystojejunostomy and the final pathological diagnosis was benign neuroendocrine tumour of pancreatic origin, staining positive for chromogranin.
The patient was readmitted to perform a duodenopancreatectomy and a neuroendocrine tumour with pancreatic origin without vascular, lymphatic, perineural or ganglionar invasion was resected with a 3 mm margin free of tumour (pT2N0Mx).

Neuroendocrine tumours are rare pancreatic tumours, with an incidence of 5 cases per million persons per year [1] that may be isolated or part of a syndrome as multiple endocrine neoplasia type I or von Hippel-Lindau syndrome, neurofibromatosis type I and tuberous sclerosis [2, 3]. In this case, the medical history was negative for congenital syndromes, thus considered to be an isolated finding.
There are two forms of neuroendocrine pancreatic tumours: the syndromic form and the non-syndromic form based on clinical and laboratory evidence of hormone production [3].
Nonsyndromic tumours are usually diagnosed later and become large, presenting with locally advanced or metastatic disease with most patients complaining of vague abdominal pain [4], as described in this case report where the clinical history and laboratory findings were negative. The liver had no evidence of secondary involvement and there was no evidence of metastatic disease elsewhere, rendering this to be classified as a locally advanced disease.
The classic CT appearance of neuroendocrine tumours is that of a hyperattenuating lesion in the arterial and venous phases. Nonsyndromic have a similar enhancement pattern as syndromic lesions, but usually they are larger and may exhibit atypical features, such as: heterogeneous enhancement in a ringlike pattern, cystic degeneration [2] or even a diffuse enlargement of the gland without contour deformity or a focal mass [5].
Lesions with cystic components represent a challenge for the radiologist as they may be confused with other cystic pancreatic tumours, such as mucinous cystadenoma/cystadenocarcinoma, serous cystadenoma, cystic papillary tumours, or even pseudocysts [6], thus leading to unsuccessful surgical internal drainage procedures (cystogastrostomy or cystojejunostomy) before definite resection. Diagnostic cyst aspiration and even biopsy of the cyst wall are also reported to be erroneous, probably because hormone levels in cystic fluid are frequently undetectable and the histological arrangement of small nests of tumours cells within the cyst wall may lead to sampling errors [7].
In this case report, even though the imaging findings showed a complex pancreatic cystic lesion and the patient reported no previous history of pancreatitis, management was based on the aspiration findings. Here we highlight that atypical pancreatic cystic lesions may represent rare endocrine tumours and so the radiologist should be aware of the limitations of fine-needle procedures in establishing this diagnosis, where sampling of the solid component should always be obtained before surgery, to avoid inaccurate patient handling.