EVEN IN CASE OF A ‘SIMPLE’ PNET…ONE NEVER KNOWS WHAT TO EXPECT

Aims Pancreatic neuroendocrine tumors (pNETs) are known for their unpredictable behaviour. Even in case of apparent disease stability, progression of the disease must always be suspected.

Methods We describe the case of a patient with a surgically treated pNET with no signs of recurrence, with late liver metastases which were diagnosed only after biopsy since previous imaging modalities were inconclusive.

Results During a routine abdominal ultrasound (US) in a 61 y.o. male patient, a 6 cm mass in the pancreatic body was detected. A subsequent CT-scan confirmed the finding and EUS-FNA made the diagnosis of G1 NET with a ki67 < 1%. The patient’s blood tests were normal, Chromogranin A was elevated (around 500 U/L) but the patient suffered from chronic gastritis and was on PPIs. After a 68Gallium-PET which excluded other localizations of the disease, the patient underwent body-tail pancreatectomy + splenectomy (R0 margins) with histological confirmation of G1 NET. After a 2-years silent follow-up, a CT scan revealed a single 6 mm hyperenhanced focal liver lesion in s6: a diagnostic work-up with MRI described the lesion as a focal nodular hyperplasia with visible central scar and a new 68Gallium-PET was negative.

Despite all these findings, we decided to perform a US-guided percutaneous biopsy of the lesion: the histology revealed a G3 well-differentiated NET with a ki67 of 25%. The patient then started somatostatin analogues (SSAs) at high doses and the focal lesion was treated with percutaneous ablation via microwaves. After almost 2 years now, the patient is fine with no signs of recurrence and still on SSAs. Monitoring is now made with blood tests every 6 months (Chromogranin A is still elevated) and a yearly CT.

Conclusions “Tissue is the issue” in the diagnosis and management of pNETs. Disease upgrading and upstaging is possible and must be addressed with the right tools and timing.