Pseudopapillary solid epithelioma of the pancreas is a rare low-grade malignant tumor of the pancreas, which has been studied and understood in recent years as the number of cases has been increasing. In this paper, we studied and analyzed cases with pathological diagnosis of pancreatic pseudopapillary solid epithelioma admitted to our hospital from June 1994 to June 2003. In 5 cases, the pancreatic tumor was found due to physical examination without conscious symptoms; 13 cases had mid-upper abdominal pain and 2 cases presented with low back pain; 3 cases were combined with gastrointestinal symptoms of fullness and nausea after eating, and another case presented with sudden high small bowel obstruction; 7 cases could find a mid-upper abdominal mass; one 56-year-old patient was combined with type II diabetes mellitus, and another case also had left renal malformation tumor. The interval between the onset of symptoms or detection of the tumor and admission to the hospital ranged from 1 day to 3 years. The abdominal mass was clearly demonstrated by either ultrasound, CT or MRI, but all of them were diagnosed as pancreatic cancer, pancreatic cystic cancer, pancreatic pseudocyst, or even as retroperitoneal tumor only because the mass was too large to identify the source. In 12 cases (57.1%), the tumor was located in the head of the pancreas and in 9 cases (42.9%) in the tail of the pancreatic body. The mean diameter of the tumors was 9.5 (3-20) cm. one 11-year-old patient had liver metastases and 13 cases had adhesions to surrounding tissues. four of the 12 pancreatic head tumors were resected with pancreaticoduodenal resection and one of them also had partial resection of the infiltrating portal vein and two metastases in the liver; the other eight cases had resection of the mass and one of them had palliative resection within the envelope due to close adhesions to surrounding vascular organs. In one case, the tumor invaded the left kidney and the left nephrectomy was performed at the same time. One case had undergone dissection in an outside hospital and had a pathological diagnosis of pancreatic pseudopapillary solid epithelial tumor; 14 cases had a clear intraoperative frozen pathological diagnosis; three other cases were reported as insulinoma or other malignant tumors by frozen, and the diagnosis was finally clarified by paraffin section and enzyme assay. The enzyme assay was positive in 14 out of 15 cases of NSE and weakly positive in 1 case; positive in 8 out of 10 cases of Vimentin, weakly positive in 1 case and negative in 1 case; positive in 7 out of 8 cases of PAS and negative in 1 case; negative for cytokeratin (CK), epithelial membrane antigen (EMA) and chromophobe granulocyte A (CHG). Eighteen cases were followed up, with a follow-up rate of 85.7% and a median follow-up time of 24 (1~60) months. All patients survived, and no signs of tumor recurrence were observed. Discussion Pseudopapillary solid epithelioma of the pancreas is a rare pathological type of pancreatic tumor originally reported by Frantz in 1959, so it is also called Frantz tumor. It is also known by various names such as papillary cystic solid tumor of the pancreas, solid cystic papilloma of the pancreas, and papillary cystic solid tumor of the pancreas. In the past 40 years or so, probably only nearly 500 cases have been reported in the English literature, and more than 20 cases have been reported in China, 2/3 of which were reported in the last 10 years. It accounts for 0.2-2.7% of pancreatic exocrine tumors in all age groups in adults, with a high incidence in Asians, and Lam et al. reported an incidence close to 2.5% in Chinese in Hong Kong. However, it can account for 1/3 to 1/2 of pediatric pancreatic tumors. Patients with pancreatic pseudopapillary solid epithelial tumors are mostly adolescent girls and young women, but men can also be involved; 20-40 years is the age of predilection, and 1/5 of patients are children, but it can be seen in all age groups, including the elderly. The mean age of this group was 27.3 years, younger than the 39 years (24 cases) reported by Martin et al. and the 32 years (9 cases) reported by Yoon et al. Mid-upper abdominal pain and abdominal mass were the most common symptoms, and jaundice rarely occurred due to biliary obstruction, and there were no signs of pancreatic endocrine dysfunction. One case in this group had high small bowel obstruction as the first symptom, and similar reports have not been seen at home or abroad. Another 56-year-old patient in our group had a 5-year history of type II diabetes mellitus, and a pancreatic tumor was found on physical examination during the course of diabetes mellitus treatment; we believe that diabetes mellitus was not directly related to her pancreatic pseudopapillary solid epithelioma. Once symptoms appear or a large pancreatic tumor is found, medical and surgical treatment is often sought quickly, but the actual course of the disease must be more prolonged. Because of the large size of the mass, it can be detected by general imaging. Ultrasound, CT or MRI can show well-defined, unevenly textured, cystic and solid lesions in the pancreas, but sometimes the origin of the tumor is not clear because it is too large or invades the surrounding organs. The tumor can occur in any part of the pancreas, and some authors [3] have suggested that it is more likely to occur in the head of the pancreas, with a slightly higher incidence of masses in the head of the pancreas in our group. The volume was large, even up to 30 cm, with an envelope, or partially enveloped. The tumor contains multiple irregular cystic cavities interspersed with solid lesions, with soft jelly-like material or friable tissue within the cavities, often with foci of bleeding. There may also be areas of firm fibrosis within the tumor. Multiple layers of tumor cells can be seen arranged around blood vessels forming a papillary structure, but this pseudo-papillary structure may be mistaken for trabeculae, and together with positive neuron-specific enolase (NSE), it is easy to diagnose this as a pancreatic endocrine tumor, but vimentin positivity and a1-antitrypsin positivity do not support this. In addition there can be a1-antitrypsin (a1-AT) positivity, progesterone receptor (PR) and estrogen receptor (ER) positivity in some patients, but cytokeratin (CK) negativity, epithelial membrane antigen (EMA) negativity, chromogranin A (CHG) negativity. There can be a variety of cell growth patterns within the tumor, and the presence of peripheral vein invasion, nuclear atypia, and numerous mitotic and necrotic cell nests are suggestive of malignancy if seen. To date, the tissue origin of pancreatic pseudopapillary solid epithelioma remains controversial and may originate from pancreatic ductal epithelium or pancreatic alveolar cells, while some authors have suggested that it originates from germinal crest-ovarian progenitor-associated cells attached to the pancreas in early embryonic life. abraham et al. found that 90% of tumors have mutational activation of the b-catenin oncogene, and this can be used to classify pseudopapillary solid epithelioma from pancreatic ductal carcinoma. Although the tumor is large and may infiltrate the surrounding tissues, it should be treated aggressively with surgery because complete resection of the lesion can lead to long-term tumor-free survival and, if necessary, reconstruction by portal vein resection or arteriotomy. 15% of cases can develop metastases, mainly to the liver, but most metastases can be removed together and are rarely directly life-threatening. There is no data showing a definite role for chemotherapy and radiotherapy, and there is no basis for the need for endocrine therapy because there is no overexpression of estrogen and progesterone receptors. In conclusion, pancreatic pseudopapillary solid epithelioma should be highly suspected in young women presenting with large tumors of the pancreas. As a low-grade malignant tumor, it has unique pathological characteristics, and aggressive surgical treatment can lead to a more favorable prognosis.