Pancreatic polypeptidoma

　　1. Etiology

　　Due to the secretion of large amounts of pancreatic polypeptide by PP cells in the pancreas, the pathological manifestations caused by pancreatic polypeptide are produced.

　　2. Pathogenesis

　　After PP was isolated by Chance, Kimmel, and Pollack in 1972, some reports have been made on its physiological effects. PP levels increase significantly after meals and can last up to 6 to 8 hours. The biological function and the physiological significance of the increase after meals are not yet clear, and it may be related to the regulation of postprandial enzymes, preventing excessive or prolonged secretion of digestive juices, and playing a certain degree of 'braking' role. Nevertheless, the current understanding of its physiological effects is limited. Greenberg et al. believe that PP's physiological role in humans is to inhibit gallbladder contraction and promote pancreatic juice secretion.

　　PPoma is mostly located in the head of the pancreas, less in the body and tail, and a few patients have tumors distributed in extrapancreatic organs. The tumors often have a complete capsule, and bleeding, necrosis, and cystic changes may be seen in the cut surface; the tumor mass is often large, with a diameter of more than 5cm; the tumor is often solitary. The disease is mostly malignant, with a small part being benign tumors or merely hyperplasia of PP cells. The common metastatic sites of malignant PPoma are the liver, but they can also metastasize to the lung, brain, and bone. By immunohistochemical methods, using a variety of gastrointestinal hormone antisera for examination, the highest content of PP can be seen, while other gastrointestinal hormones are negative or weakly positive. The determination of PP in the tumor tissue shows a very high content, up to 196.5μg/g wet tissue, while the content of other gastrointestinal hormones is very small or negative. Electron microscopy examination shows that the granular morphology of tumor cells is consistent with that of PP granules.

　　Pancreatic polypeptideoma often presents with an enlarged head of the pancreas, which can compress the portal vein, biliary tract, and cause corresponding clinical symptoms, such as abdominal pain and masses. Other complications include: symptomatic diabetes, a few patients present with symptoms of diabetes at the onset of the disease. Therefore, if diabetic patients have persistent abdominal pain, or elderly patients suddenly develop diabetes, or if patients with pre-existing diabetes suddenly worsen their condition in recent days, they should be vigilant about the possibility of this disease. Thrombophlebitis, in the late stage of pancreatic polypeptideoma, patients may develop migratory thrombophlebitis or arterial thrombosis.

　　The clinical manifestations of PPoma have no obvious relationship with the excessive secretion of PP. Most cases of PPoma have no obvious symptoms. Some patients with PPoma may show symptoms of WDHA syndrome, such as diarrhea (watery diarrhea or accompanied by steatorrhea), which may be mild or severe. Individual cases may have symptoms similar to watery diarrhea, hypokalemia, and hypochlorhydria syndrome as in VIPoma; through the determination of serum and tumor tissue PP and VIP, the level of PP in the blood increases more than 1000 times, while VIP is not high, so it is considered that PP can also cause symptoms such as watery diarrhea and steatorrhea. In addition, since PP cells are mainly distributed in the head of the pancreas, PPomas often present with an enlarged head of the pancreas, which can compress the portal vein, biliary tract, and cause corresponding clinical symptoms, such as abdominal pain and masses. In clinical practice, abdominal pain and masses may occur.

　　Pancreatic polypeptideoma is one of the gastrointestinal endocrine tumors, mainly occurring in cells containing pancreatic polypeptide (PP) in the endocrine cells of the pancreas, and is extremely rare in clinical practice. The etiology of the disease is unclear, so there is no effective preventive method. Early detection, early diagnosis, and early treatment of the disease are of great significance for the prognosis of the disease. The treatment principle after diagnosis is still mainly surgical treatment.

　　1. Serum PP immunodetection is an important indicator for the diagnosis of this disease. The fasting serum PP level of patients with this disease is usually 20 to 50 times higher than normal, and some even exceed 700 times. However, with the widespread implementation of PP immunodetection, it has been found that 30% to 70% of various islet endocrine tumors can be accompanied by PP cell hyperplasia and increased peripheral blood PP concentration, suggesting that PP is a tumor marker for islet endocrine tumors, or PP cells may be the more early stage of islet endocrine cells, with stem cell characteristics.

　　2. Localization diagnosis can rely on ultrasound, CT, MRI, and selective angiography, etc., which are helpful to understand the location, size, number, and whether there is metastasis of the tumor. Glaser et al. proposed that percutaneous transhepatic portal vein sampling can be used to determine the location of PP production, which is helpful for tumor localization.

　　Patients with pancreatic polypeptideoma should have a light diet, avoid spicy and irritating foods. According to different symptoms, there are different dietary requirements. It is recommended to consult a doctor for specific dietary standards tailored to specific diseases.

　　1. Treatment

　　Since PPoma usually has no hormone-related symptoms, the treatment is mainly aimed at the tumor itself. Therefore, surgical treatment is the preferred treatment method for this disease. Even if metastasis occurs, surgical removal of the metastatic lesion can still relieve symptoms, normalize biochemical indicators, and even possibly cure the disease. For patients with advanced stage tumors that cannot be removed, chemotherapy with streptomycin can be used. Chemotherapy can alleviate symptoms or partially alleviate them, and even normalize the serum PP level.

　　2. Prognosis

　　The malignant trend of pancreatic polypeptideoma is significant. Even in cases where there are no symptoms and the serum level of pancreatic polypeptide has been elevated for several years, it can develop into a malignant tumor with metastasis and eventually lead to death. In cases with slow progression and those with advanced stages that have already been treated with surgery or have metastasis, they can still survive for several years. There are 12 documented cases of this disease, with the course of the disease ranging from 1 month to 7 years before treatment, and there are also patients who have survived for 2 to 3 years after starting treatment.