Renal malformation tumor, also known as renal vascular smooth muscle lipoma (ANGIOMYOLIPOMA), is a benign tumor of the kidney, consisting mainly of thick-walled aneurysmal vessels, smooth muscle, and varying degrees of mature adipose tissue. It is less than 10% of renal tumors. The age of onset is mostly 20-50 years old, and it is more common in females. Most of them are found on physical examination and then presented to the doctor, while a few patients come to the doctor because of spontaneous bleeding from malformation tumor producing symptoms such as back pain or shock. The incidence has been increasing in recent years, which may be related to the improvement of diagnostic techniques. How is renal malformation tumor diagnosed? Most renal malformation tumors are diagnosed by ultrasound during physical examination and then by further CT or MRI examination of the kidney. The diagnosis of renal malformation tumor is basically confirmed by ultrasound, MRI or CT examination if there is a fatty component in the tumor, because renal cancer does not have a fatty component. Renal malformation tumor varies greatly from tumor to tumor due to the different content of its components, especially fat content, which leads to preoperative misdiagnosis. The following cases are easy to be misdiagnosed as renal carcinoma and should be carefully identified: (1) tumor with more bleeding and increased tumor density, which conceals the adipose tissue; (2) tumor diameter of 1,0-1,5 cm, which cannot reflect the true density of tumor due to the volume effect; (3) renal malformation tumor with mainly vascular smooth muscle tissue and very small amount of adipose tissue. According to my experience for suspected renal malformation tumor, CT thin-layer scan, or MRI with increased pressure lipid sequence can be used to help the diagnosis if the fat component is measured to improve the correct diagnosis rate. How is renal malformation tumor classified? There are two main categories of renal malformation tumors. One is non-hereditary malformation tumor, which is usually a separate disease, and the tumor is mostly a solitary lesion, and most patients fall into this category. The other type is hereditary malformation tumor, which may be associated with tuberous sclerosis. This is a familial disease inherited from autosomal dominant genes, and 80% of patients have butterfly-shaped sebaceous adenoma on the face and other organs such as brain, eye, bone, heart and lung. Delayed brain development, poor intelligence, and seizures are also characteristic of the disease. Renal tumors are clinically characterized by multiple foci in both kidneys, and 80% are female, with symptoms appearing between the ages of 20 and 50, with the majority occurring after the age of 40. How to choose renal malformation tumor treatment? Treatment options for renal malformation tumors include watchful waiting, selective renal artery embolization and surgical procedures. The purpose of surgery is to remove the tumor, relieve the symptoms caused by the tumor, prevent spontaneous rupture, preserve the renal unit, and exclude the possibility of imaging suspicion of malignancy. 1. For asymptomatic tumor patients with a clear diagnosis of mismatched tumor <4cm in diameter, observation without necessarily treatment can be performed, and annual CT or ultrasound examination to understand tumor changes is sufficient. If there are symptoms or complications, such as bleeding, pain, hematuria, infection, fluid accumulation, etc., they should also be treated surgically. For those who are suspected to have malignant tumor but have difficulty in preoperative diagnosis, they should be actively investigated by surgery and can be treated by surgery according to the results of frozen section examination without follow-up. 2. According to the size and location of the tumor, tumor removal, partial nephrectomy or nephrectomy should be performed. Because the occurrence of renal malformation tumor is multi-centered and there are more chances that both kidneys occur simultaneously or successively, kidney-preserving surgery should be performed as much as possible to preserve normal kidney tissues as much as possible, and the kidney should not be easily removed during surgery; 3. For large malformation tumors with bleeding, they are often closely adhered to the surrounding organs, and most of them can only choose to remove the kidney because it is difficult to perform tumor enucleation or partial nephrectomy, so for malformation tumors that tend to bleed Therefore, for the misshapen tumor which is easy to bleed, it is better to choose active treatment to avoid treatment after bleeding and increase the difficulty of kidney preservation surgery; 4.misshapen tumor with acute bleeding and unstable vital signs or tumor with multiple, especially huge tumors which cannot be surgically removed can first consider selective renal artery embolization, which is mostly used for super-selective renal artery branch embolization to protect part of the renal function, and for those with acute bleeding, the bleeding will stop after embolization and the clot will be mechanized and the surrounding organ adhesions will improve. For patients with acute hemorrhage, when the hemorrhage stops after embolization and the adhesion between the clot and the surrounding organs improves (usually 3 months after hemorrhage), then consider surgery to remove the tumor; 5.