I. Background Lymphangioma is a tumor-like lesion of the lymphatic system with confusing clinical and pathological names, some are called lymphangioedema or cystic hydatid cyst, and some are called simple lymphangioma or cystic lymphangioma. The disease is more likely to occur in younger individuals, such as infants and children. Lymphangioleioma can occur congenitally, often due to abnormal congenital development of lymphatic vessels, failure of the primitive lymphatic sac to return to the central vein, abnormal enlargement of isolated lymphatic vessels or lymphatic sacs due to abnormalities in normally differentiated lymphatic structures or failure to establish contact with normal drainage channels. The lymphatic vessels can also be blocked by infection, tumor, trauma, surgery or degeneration of local lymph nodes and other acquired factors, resulting in a gradual increase in the diameter of the vessels. Lymphangioleiomas are more common in the face, neck, axilla, shoulder and groin, and less common in the trunk, and even less common in the retroperitoneum. The present case of retroperitoneal lymphangiectasia with extensive invasion of the pancreas and duodenum has not been reported in the literature. Basic information and medical history The patient, male, 29 years old. He was admitted to the hospital on 2014-7-30 due to “retroperitoneal occupancy found on physical examination for 1 month”. Examination: T 36,5℃, P 75 times/min, R 15 times/min, BP 120/70 LHg (1 LHg=0,133Kpa). Specialized examination: abdomen was flat and soft, no obvious masses were palpated throughout the abdomen, liver and spleen were not detected under the ribs. Abdominal percussion showed drum sound and normal bowel sounds. Laboratory tests and imaging examinations Laboratory tests: routine blood, liver function, kidney function and electrolytes were normal, CEA, AFP and CA19-9 were normal. Abdominal ultrasonography: a slightly strong echogenic reticular structure with a range of 12,6 cm×6,2 cm was seen in the right upper abdomen from the level of the hepatic portal to the level of the umbilicus. CT examination of the whole abdomen: a cystic foci with interstitial growth was seen in the right abdomen and retroperitoneum, and small penetrating vascular shadows were seen in the enhanced scan. The lesion was clearly demarcated from the surrounding structures, and the possibility of lymphangioleiomyomatosis was considered. Abdominal MRI examination: irregular mass-like shadow was seen in the abdominal cavity and retroperitoneum, with slightly low signal in T1WI and high signal in T2WI, with inhomogeneous signal and still clear border, size 12, 3 cm×7, 1 cm×6, 8 cm. 3.Surgery and pathology Intraoperatively, a huge right retroperitoneal tumor was seen, with soft texture, unclear boundary and no obvious envelope. The posterior edge of the tumor involved the posterior aspect of the pancreatic hook and hepatoduodenal ligament, which compressed the portal vein and could not be detached completely, so pancreaticoduodenectomy was performed. After complete resection of the tumor, the specimen was dissected and contained old blood and a small amount of clear fluid. Gross pathology: a mass was seen on the proximal side of the intestinal canal, measuring 11 cm × 8 cm × 5 cm, with a smooth surface and a foveal cut surface, grayish red and grayish yellow, containing bloody fluid. The mass could not be detached from the intestinal wall and pancreas. Microscopic pathology: the tumor tissue consisted of ductal lumens of different sizes, some of which were irregular in morphology and communicated with each other, with erythrocytes and lymphatic fluid visible in the lumen and a single layer of flattened epithelium lining the ductal wall. Lymphocyte aggregates were seen in the interstitium. Pathological report: “retroperitoneal mass” was a spongy lymphadenoma. Tumor tissue was seen in the myenteric layer of the intestinal wall and the pancreas, and no tumor tissue was seen in the cut edges of the stomach and intestine. 4. Postoperative management and prognosis The patient’s vital signs were stable within 24 h after surgery, and he was not admitted to the intensive care unit for treatment. The gastric tube was removed on the first day after surgery, and normal exhaustion and defecation resumed on the second day after surgery. The patient was discharged 2 weeks after surgery without any perioperative complications. The patient was followed up for 6 months without any complications and is still being followed up. Although retroperitoneal cavernous lymphangiectasia is a benign lesion, its growth is invasive and its proliferating endothelial cells can slowly invade or compress the surrounding tissues, leading to atrophy of the normal tissue structure of the surrounding organs and consequently to dysfunction. The lymphangioleioma grows along the lax tissue space, and its morphology coincides with the local space in a lobulated shape. “lobulated”. Spongy lymphangioleiomyolipoma shows a cellular tortuous and dilated cystic structure with often irregular margins, extending and encapsulating along the surrounding tissue interstices, with poor demarcation between the lesion and adjacent tissues, and mild enhancement of the cystic wall and separation after enhancement. The imaging presentation of this case is basically consistent with the above characteristics. Since retroperitoneal lymphadenoma is rare, even though the existing advanced diagnostic techniques (such as HRCT, etc.) are commonly used in large tertiary hospitals, preoperative diagnosis is still difficult if there is a lack of puncture pathology or insufficient clinical experience. Therefore, once retroperitoneal cavernous lymphangiectasia is diagnosed or highly suspected, surgical treatment should be considered. During surgery, disconnecting and ligating the fascia, lymphatics and small vessels connected to the tumor, stopping bleeding and ligating at the same time can reduce the risk of intraoperative bleeding, postoperative tumor recurrence and occurrence of celiac leakage. Proper separation and protection of peritumor tissues are also required. In this case, the retroperitoneal mass was located in the right upper abdomen, because the retroperitoneal tumor in this area could squeeze and push the hepatic artery, portal vein and common bile duct in the hepatoduodenal ligament, push the head of pancreas and superior mesenteric artery and vein, and often compress or displace the inferior vena cava and renal vein. Therefore, it is easy to cause damage to these tissues during surgery, which makes resection more difficult. In this case, the retroperitoneal mass involved the posterior aspect of the pancreatic hook and hepatoduodenal ligament, compressed the portal vein, and densely wrapped the duodenum and the anterior and posterior aspects of the head of the pancreas, which could not be completely detached, so pancreaticoduodenectomy was performed. The gap between the posterior margin of the pancreas and the superior mesenteric vein should be completely freed, the portal vein trunk should be carefully protected, and the gastroduodenal artery should be firmly ligated. The upper and lower margins of the pancreas and the bleeding point should be carefully sutured during the dissection of the pancreas, and the main pancreatic duct should be carefully searched and a supporting drainage tube should be placed. Finally, the anastomosis must be carefully sutured during the reconstruction of the digestive tract to reduce the occurrence of postoperative anastomotic leakage. Since the establishment of the pancreatic surgery group in 2007, our institute has been mainly engaged in the surgical treatment of various benign and malignant lesions, mainly pancreatic tumors, tumors of the lower bile duct and tumors of the jugular abdomen. After years of accumulation, we have a complete set of perioperative management strategies, including preoperative diagnosis strategy, resectability assessment strategy, nutritional support strategy, obstructive jaundice management strategy, coagulation monitoring and management strategy, prophylactic antibiotic application strategy, perioperative fluid therapy strategy, postoperative pancreatic fistula monitoring and prevention strategy, preoperative cardiopulmonary exercise and assessment strategy, and analgesic management strategy. . The concept of accelerated recovery in pancreaticoduodenectomy (ERAS) application has now been refined. Statistically, from July 2008 to December 2014, our group completed 281 cases of pancreaticoduodenectomy, of which more than 90% were postoperatively diagnosed as pancreatic head tumor, duodenal tumor and lower bile duct cancer. The present case of retroperitoneal cavernous lymphadenoma undergoing pancreaticoduodenectomy is very rare, and only one case was found in the literature. Therefore, a retrospective analysis and a review of the literature were conducted in the hope of bringing benefits to the clinical work of clinicians.