Pancreatoblastoma

Pancreatoblastoma is a rare embryonal tumour of the pancreas, and the commonest pancreatic tumour in children under 10 years. It also occurs, rarely, in adults, in whom the course is more aggressive.

The median age in children is about 4 to 5 years, with a slight male predominance. Associations are Beckwith-Wiedemann syndrome and familial adenomatous polyposis. Tumours are large (7 to 18 cm), encapsulated and often in the head. Liver metastases occur in about a third at diagnosis. The 5-year survival is about 50% to 80% in children after resection.

Alpha fetoprotein is raised in a third to two thirds of cases and is a useful marker.

Pathophysiology.

Tumour cells show acinar, ductal and neuroendocrine differentiation, with characteristic squamoid corpuscles. Alterations of Wnt signalling (CTNNB1 and APC) and loss of heterozygosity at chromosome 11p are common.

Abdominal mass, pain, vomiting, weight loss, jaundice, diarrhoea and failure to thrive. Cushing syndrome and the lipase hypersecretion syndrome are rare. Adults present with pain and weight loss.

Red flags.

• Rapidly growing abdominal mass.
• Jaundice or obstruction.
• Liver metastases.

Ultrasound, CT and magnetic resonance imaging show a large, well defined, heterogeneous mass with solid and cystic components and septa. Serum alpha fetoprotein is raised. Biopsy (endoscopic ultrasound or percutaneous) confirms the diagnosis, with immunostaining for acinar, ductal and neuroendocrine markers and nuclear beta catenin. Stage with chest CT and consider genetic testing for syndromes.

Differential diagnosis.

• Solid pseudopapillary neoplasm.
• Neuroblastoma.
• Wilms tumour.
• Hepatoblastoma.
• Pancreatic neuroendocrine or acinar cell tumours.
• Lymphoma.

Complete surgical resection is the key to cure and is feasible in many cases. Neoadjuvant platinum based chemotherapy (cisplatin with doxorubicin, and in some regimens etoposide or ifosfamide) shrinks unresectable tumours and treats metastases. Doses are set by body surface area or weight by the paediatric oncology team. Radiotherapy is used for incompletely resected local disease. Resect or ablate liver metastases when possible.

Treat pancreatic exocrine insufficiency with enzyme replacement as needed.

• Pancrelipase: 500 to 1,000 lipase units/kg with each main meal in children (25,000 to 50,000 lipase units in adults), half with snacks; maximum 10,000 lipase units/kg daily; monitor growth, stool and abdominal symptoms; reduce if over 10,000 units/kg daily.

Monitoring. Alpha fetoprotein and imaging every 3 months for 2 years, then every 6 months, since relapse is common within 2 years.

Referral and escalation. Paediatric oncology and surgery at a specialist centre; genetics for syndrome screening.

Special groups. Children need weight based dosing and long term follow up for late effects. Adults have worse outcomes and need an early multidisciplinary plan.