Solid serous cyst adenoma of the pancreas: An unusual presentation to have in mind

Clinical History

A 49-year-old female patient came to the emergency department for non-specific mild upper abdominal pain, which she had been feeling for almost 1 year. The patient presented no other notable symptoms.
Clinically and analytically we had no evidence of a clear, aggressive, malignant process, or of an acute abdominal pain syndrome.

Imaging Findings

An US abdominal study showed cholelithiasis, and at the body of the pancreas a hypoecogenic, apparently solid lesion, of approximately 2 cm was seen.
A dynamic CT study was performed. A nodular intrapancreatic image was seen at the junction of the neck and body. It was hyperdense in the arterial phase, with a quite homogeneous and early enhancement; with a lasting mild enhancement in relation to the pancreatic parenchyma in the portal venous phase. The lesion had well defined and discretely lobulated borders.
MRI showed that the pancreatic lesion had low intensity in T1 sequence, moderately high intensity in T2 with fat suppression sequence. After the administration of gadolinium, it had intense enhancement in the arterial and venous portal phase and even a mild enhancement in the late phase.
Splenopancreatectomy of the body and tale was performed. The histological diagnosis was of a microcystic serous cysto-adenoma at the body of the pancreas.

Discussion

The increasing use of CT as a diagnostic tool shows the existence of a large amount of asymptomatic cystic pancreatic lesions. It is important to differentiate between benign cystic pathology and malignant, as we know that management, treatment, and prognosis are entirely different [1][2].
Serous cyst adenoma is in the benign cystic tumours group. It is known to have three usual patterns of presentation: Polycystic, honeycomb and oligocystic. A quite atypic presentation is solid serous cyst adenoma, which is histologically formed by microcysts separated by trabeculae and fibrous bands. This predominantly solid internal structure translates to diagnostic imaging as having a solid appearance, distant from the usual predominantly cystic patterns, thus leading to diagnosis confusion .
US is generally the initial test. The next step is usually CT, as it gives us a good characterisation of the lesion, and secondary findings. MRI serves to better define the imaging characteristics, and ecoendoscopy helps differentiate a solid from a cystic lesion and to characterise its internal structure [3][4].
The imaging appearance at the US, CT, MRI and ecoendoscopy was of a solid lesion suggestive of a hypervascular tumour, but with a lack of findings secondary to a malignant neoplasm [5]. Still, by frequency we would have thought of a neuroendocrine tumour [6]. Other rare possibilities that we must have in mind, and that are more compatible with the finding in this case, are in the mimicking hypervascular lesions group, such as solid presentation of serous cyst adenoma, ectopic intrapancreatic spleen or a hypervascular tumour metastasis. The radiological differentiation between a neuroendocrine tumour and solid serous cystadenoma is quite difficult and the final diagnosis is almost always made by the pathologist [7].
It is usual that this atypical presentation of serous cyst adenoma ends up in surgery. Otherwise, it translates into an increased rate of secondary complications.
In this particular case, the patient developed fluid collections posterior to the procedure and was discharged after three weeks.
So, in front of a solid hypervascular pancreatic tumour, the usual diagnosis is a neuroendocrine tumour, but there are also mimicking hypervascular lesions, such as atypical presentations of cystic lesions, intrapancreatic ectopic spleen, and hypervascular tumour metastases possibilities to know and to keep in mind with such findings.

Differential Diagnosis List

Final Diagnosis

Solid serous cyst adenoma of the pancreas.

URL:	https://www.eurorad.org/case/10217
DOI:	10.1594/EURORAD/CASE.10217
ISSN:	1563-4086