Pancreatic neuroendocrine tumours (pNET) are considered rare lesions with an incidence of less than 1 per 100 000 person-years. Five-year survival is about 55% when the tumours are localized and resected, but only about 15% when the tumours are not resectable (1). In advanced stages of this disease, as many as 50% of the patients with pNET have already developed metastases in the moment of initial diagnosis, whilst the presence of liver metastases is the major determinant of survival (2). We present a case of a neuroendocrine tumour of the pancreas with liver metastases, imaged with grey-scale, colour Doppler, contrast-enhanced ultrasound (CEUS) and endoscopic ultrasound.
Even though pNETs carry a better prognosis as compared to adenocarcinoma of the pancreas, approximately 90% are silent and non-functional; therefore, most patients are diagnosed in late stage and present metastatic (60%) or locally unresectable advanced disease (21%) with a poor prognosis (3). A specific feature of this case was the presence of cystic metastases of the liver, some with internal septations and some with solid content. Most hepatic metastases are solid, but some have a complete or partially cystic appearance. Hypervascular metastatic tumours with rapid growth may lead to necrosis and cystic degeneration. This mechanism is frequently demonstrated in metastases from neuroendocrine tumours, sarcoma, melanoma, and certain subtypes of lung and breast carcinoma (4).
For this case, CEUS supported the diagnosis of cystic metastases, whilst studies showed previously that CEUS represents a useful method in clinical practice and clearly improves the differential diagnosis between malignant and benign liver lesions detected on standard ultrasonography, with a positive predictive value of 95.4% and negative predictive value of 95.9%. The main criteria for malignancy on CEUS is contrast wash-out in the late portal venous phase whereas benign lessons typically remain iso-enhancing with the surrounding normal liver tissue (5,6). Metastases usually show a brief arterial hypervascularity and complete rapid wash-out, which can improve detection during the portal phase (7).
Neoplastic cysts such as cystic metastasis can be characterized on CEUS by sensitive real-time demonstration of vascular flow within the septa or solid component. Non-neoplastic complex cysts such as hemorrhagic cysts or hydatid cysts show the absence of intralesional enhancement on CEUS, thus confirming their non-neoplastic nature (8).