Pancreatic rare tumours
Pancreatic rare tumours
Pancreatic neuroendocrine neoplasms (PanNENs)
Pancreatic neuroendocrine neoplasms (PanNENs) have their origin in the hormone-producing cells of the pancreas. It is also known as the islet cell tumour, as neuroendocrine cells of the pancreas are displayed in islets (islets of Langerhans – see Introduction to the pancreas for more details).
PanNENs can be named based on whether they are functioning (making hormones that cause symptoms) or non-functioning (not making hormones).
- Functional tumours maintain the cellularity functions and produce a hyper secretion of the hormone the cellular type affected by the tumour process is supposed to synthesize. Hyper secretions of the different hormones (for example insulin, gastrin, glucagon, etc.) have their own signs and symptoms and are frequently detected in early stages because of the high levels of hormones in the blood. Tumours like insulinomas and gastrinoma belong to the type of functional PNETs.
- Nonfunctional tumours do not produce excess of hormones making difficult its diagnosis. Symptoms depend on the spreading and the growth rhythm and often do not show any alarming sign. They normally belong to malignant type of cancers.
Recently, the WHO3 has classified this type of tumours into 2 categories:
- Well differentiated neuroendocrine tumours (WDNET): WDNETs are usually slow growing even when they are metastatic but they do not respond to therapy well. They can be graded in 1, 2 or 3 depending on the stage of invasion but even when they are G3, prognosis is better than in PDNEC.
- Poorly differentiated neuroendocrine carcinomas (PDNEC): PDNECs are defined by default grade 3 with highly aggressive behaviour. They are defined by the morphology and they are very aggressive clinically. These tumours show sensitivity to cisplatinum treatments but unfortunately recur soon after.
Pancreatoblastoma is described as a very rare childhood tumour originated from epithelial exocrine cells in the pancreas. It affects mainly young children with a mean age of 5 years old4. It affects primarily stem cells in the pancreas so it can appear in many different cell type differentiations, such as acinar cells, ductal cells, mesenchymal cells, neuroendocrine cells, etc. This variety makes it a non-specific tumour. It is a slow growing tumour even its diversification makes it difficult to diagnose.
Pancreatoblastoma are initially suspected when the tumour marker alpha-fetoprotein is higher than expected for a healthy person. Afterwards, imaging tests are performed to determine the exact location and size of the tumour, if it has spread to other organs and study the removal with surgery when possible.
A small sample of the tumour (biopsy) may be obtained for examination under a microscope through a technique called fine-needle aspiration. From the histological analysis of this sample, a differential diagnosis from other pancreatic tumours is done based on the characteristic accumulation of squamous cells in the shape of nests, composed of a spiral conglomerate of spindle cells.
Solid pseudo-papillary neoplasm (SPN)
Solid pseudo-papillary neoplasm (SPN) is an ultra-rare disease with few reported cases. The cell of origin for SPN is unclear. Even it has been described as a carcinoma in the past, its epithelial origin is dubious.
SPNs can be difficult to differentiate from PanNENs both at clinical and pathological levels. However, during the histological analysis of a sample of this tumour, SPNs show a diffuse nuclear labelling of the bio-marker beta-catenin, while keratins are negative or focal positive.
Although SPNs are classified under malignant category because of its histological grade, they exhibit a very low malignancy potential with a rare capability to metastasize. The ratio of survival after 10 years is of 95% of the patients and the little mortality reported is dubious about the accuracy of the diagnosis.5,6