1.What is retroperitoneal tumor? Primary retroperitoneal tumor (PRT) refers to tumors that originate in the retroperitoneal space and are not derived from retroperitoneal organs. 2.What are the types of retroperitoneal tumor? Primary retroperitoneal tumor can occur in any embryonic tissue, from muscle, fascia, connective tissue, fat, blood vessels, lymphatic vessels, nerve and sheath, ectopic tissue and embryonic remnants. 40%-80% originate from mesenchymal tissue, 10%-50% from neural tissue. Eighty percent of them are malignant, and benign ones have a tendency to become malignant. Benign tumors include: lipoma, smooth muscle tumor, fibroma, rhabdomyoma, lymphangioleioma, hemangioma, hemangiopericytoma, yellow granuloma, ganglioneuroma, pheochromocytoma, paraganglioma, nerve sheath tumor, neurofibroma, teratoma, chordoma, etc. Malignant tumors include: liposarcoma, smooth muscle sarcoma, malignant fibrous histiocytoma, rhabdomyosarcoma, lymphangiosarcoma, angiosarcoma, etc. Neuroblastoma, malignant pheochromocytoma tumor, malignant paraganglioma, malignant nerve sheath tumor, malignant teratoma, malignant chordoma, etc. 3 What are the clinical manifestations of retroperitoneal tumor? (1) Abdominal mass: retroperitoneal tumor is deep and asymptomatic in the early stage, but when the tumor develops to a certain extent, it will be found to have abdominal mass when it compresses the organs and causes distension and pain. Common symptoms of urinary tract compression are: urinary frequency, urinary urgency, difficulty in urination or hematuria; ureteral compression may cause hydronephrosis; lower limb edema if blood vessels are compressed. (3) Pain: The pain of retroperitoneal tumor is due to the increase of peritoneal tension or compression of invasion and stimulation of nerves, which is manifested as low back pain, perineal pain or lower limb pain. (4) Systemic symptoms: wasting, weakness, loss of food and drink, and even cachexia. A few tumors with endocrine function may show corresponding symptoms. 4.What are the traditional treatment methods of retroperitoneal tumor? At present, surgical resection is still the main method to treat retroperitoneal tumor. However, due to the large size, deep location and rich blood supply of retroperitoneal tumor, it is mostly adhered to surrounding organs, large blood vessels and nerve tissues, which results in large amount of surgical bleeding. It is difficult to remove the tumor completely in one operation, and the tumor recurrence rate is high after surgery (49-88%). Laparoscopic surgical resection is less traumatic and suitable for tumors of small size. Except for retroperitoneal lymphoma, most retroperitoneal tumors are insensitive to radiotherapy and chemotherapy. 5.How to implement cryotherapy for retroperitoneal tumor? Cryotherapy for retroperitoneal tumors is mostly performed under CT surveillance. After local anesthesia, the tumor tissue is directly punctured through the skin, and the cryoprobe is introduced into the tumor to perform cryogenic freezing. After the cryopreservation is completed, the patient lies flat for 2-4 hours. 6.What are the characteristics of retroperitoneal tumor cryotherapy (1) Small trauma, less blood loss, no blood transfusion. (2) Quick recovery, the patient can get out of bed the day after treatment. (3) High safety: it can be performed under CT surveillance, which can avoid damage to the surrounding important organs and large blood vessel structures and ensure the safety of treatment. (4) Good tolerability: done under local anesthesia, no significant pain to the patient, and can be tolerated by elderly patients.