bubble_chart Overview

Primary retroperitoneal tumors refer to tumors that originate in the retroperitoneal space and do not include tumors from the organs originally located in this area. These are relatively rare tumors, with malignancies accounting for about 70% of cases. Common benign tumors include teratomas, schwannomas, and fibromas, while malignant tumors frequently seen are liposarcomas, fibrosarcomas, leiomyosarcomas, embryonal carcinomas, neurofibrosarcomas, and cervical malignancies with cachexia.

bubble_chart Pathological Changes

The retroperitoneal space is quite extensive, extending superiorly to the diaphragm and inferiorly to the pelvic diaphragm. Tumors can originate from fat, connective tissue, fascia, muscles, blood vessels, nerves, lymphatic vessels, and embryonic remnants within this space, resulting in a wide variety of pathological classifications for these tumors, as shown in Table 24-1.

Table 24-1 Pathological Classification of Common Primary Retroperitoneal Tumors

Tissue of Origin	Benign Tumors	Malignant Tumors
I. Mesenchymal Tissue	Lipoma Fibroma Leiomyoma Rhabdomyoma Hemangioma Hemangiopericytoma Lymphangioma Mesenchymoma	Liposarcoma Fibrosarcoma Leiomyosarcoma Rhabdomyosarcoma Hemangioendothelioma Hemangiopericytosarcoma Lymphangiosarcoma Mesenchymosarcoma
II. Lymphatic Tissue	Pseudolymphoma	Malignant lymphoma
III. Neural Tissue	Schwannoma Neurofibroma Ganglioneuroma Pheochromocytoma Non-chromaffin paraganglioma	Malignant schwannoma Neurofibrosarcoma Neuroblastoma, ganglioneuroblastoma Malignant pheochromocytoma Malignant non-chromaffin paraganglioma
IV. Urogenital Origin	Mesonephroma	Malignant mixed Müllerian tumor
V. Germ Cell Origin	Benign cystic teratoma	Malignant teratoma, endodermal sinus tumor Choriocarcinoma
VI. Tissue of Origin Unknown	Cyst, adenoma	Undifferentiated carcinoma, ectopic tissue carcinoma, undifferentiated sarcoma

bubble_chart Clinical Manifestations

Except for a few retroperitoneal tumors, such as pheochromocytomas, which can secrete chemical mediators and produce obvious clinical symptoms that are easily detected early, the vast majority of retroperitoneal tumors are asymptomatic at the onset. When the tumor gradually grows, causing compressive symptoms or is accidentally discovered by the patient, medical examination is sought. The most common symptoms are abdominal masses, abdominal pain, and symptoms caused by compression or irritation of adjacent organs.

The abdominal mass is often discovered accidentally by the patient and is not accompanied by other symptoms. A few patients discover the mass simultaneously with abdominal pain. Depending on the location, size of the tumor, and thickness of the abdominal wall, the mass can range from as small as a walnut kernel or an apple to as large as a fetal head, even occupying one-fourth of the abdominal cavity. The mass is fixed, mostly broad-based, and cannot be moved. Cystic tumors often have a cystic sensation. Generally, there is no tenderness or abdominal muscle tension.

The nature of abdominal pain is mostly distending pain or dull pain, with colicky pain rarely occurring. When the tumor compresses the nerve trunks or roots of the lower limbs, it can cause buttock and leg pain. Back pain is less common. When there is internal bleeding or necrosis in the tumor, its volume may suddenly increase, accompanied by severe pain and low-grade fever. As the tumor grows and causes compression or displacement of adjacent organs, corresponding symptoms may arise depending on the location. Compression or irritation of the stomach can cause postprandial epigastric fullness, nausea, and vomiting; compression of the small intestine can lead to chronic paroxysmal periumbilical abdominal pain, abdominal distension, and fullness, resulting in incomplete bowel obstruction; irritation of the rectum can increase the frequency of bowel movements, cause tenesmus, or even lead to hematochezia if the tumor ulcerates into the intestinal lumen; compression of the ureters can cause hydronephrosis, and prolonged bilateral compression may lead to uremia; compression or irritation of the bladder can cause frequent urination, reduced urine volume per void, and urgency; compression of veins and lymphatic vessels, causing reflux obstruction, can lead to lower limb edema, abdominal wall venous dilation, scrotal edema, and varicocele; compression of the pulsating artery may also produce vascular murmurs.

Tumors with secretory functions, such as pheochromocytomas, can secrete catecholamine substances, leading to paroxysmal hypertension. Large fibrous tissue tumors may secrete insulin-like substances, causing hypoglycemic symptoms. Some rare functional mesenchymal tumors can cause hypophosphatemia due to antibiotic D, leading to osteomalacia.

When malignant tumors grow to a certain stage, symptoms such as weight loss, lack of strength, reduced appetite, anemia, fever, ascites, jaundice, or even cachexia may appear.

bubble_chart Diagnosis

Diseases and tumors of intra-abdominal organs, especially those behind the peritoneal membrane, can produce symptoms similar to those of this condition. Therefore, differentiation is often required from conditions such as splenomegaly, pancreatic cysts or tumors, renal tumors, adrenal tumors, hydronephrosis, and liver tumors. The primary purpose of using various auxiliary diagnostic techniques is to determine the location and extent of the tumor, as well as its relationship with adjacent organs. Sometimes, the nature of the tumor can also be identified. If abdominal plain films reveal structures such as bones or teeth within the tumor, it can be diagnosed as a teratoma. Fibrosarcomas, neurofibromas, or malignant schwannomas may occasionally show calcification. Enlargement of the intervertebral foramen or even bone destruction should raise suspicion of neurofibromas. Barium meal or barium enema examinations help determine the relationship between the tumor and the gastrointestinal tract, with the main signs being displacement or compression of the stomach or intestines. To assess whether the tumor is encasing or displacing the kidneys or ureters, intravenous pyelography is often necessary. In some cases, retrograde urography or even placement of a ureteral catheter may be required to facilitate identification of the ureter during surgery. In the past, invasive techniques such as abdominal aortography, inferior vena cavography, and retroperitoneal pneumography were used for tumor localization. However, with the widespread adoption of B-mode ultrasound and computed tomography (CT) scans, these methods are largely unnecessary for most patients. CT scans can precisely locate tumors, clarify their relationship with surrounding organs and major blood vessels, and even detect early local tumor recurrence.

bubble_chart Treatment Measures

Surgical intervention is the primary treatment method. Typically, tumors are only detected once they have grown to a certain size, and when they encase critical blood vessels or nerves, management becomes particularly challenging. Therefore, it is advisable to anticipate more difficulties preoperatively and prepare thoroughly, such as bowel preparation and ensuring the availability of vascular anastomosis materials and instruments. During the surgery, the first step is to determine whether the tumor is benign or malignant, which may require a seasonal epidemic frozen section examination. Next, the extent of tumor resection must be determined. If the tumor is resectable, en bloc resection should be pursued, avoiding piecemeal resection or leaving residual tumor tissue behind. If there is a partial defect in the abdominal stirred pulse wall, it should be repaired or reinforced with synthetic mesh to prevent postoperative formation of a stirred pulse aneurysm rupture. When the mesenteric membrane superior stirred pulse trunk needs to be resected simultaneously, a splenic stirred pulse mesenteric membrane superior stirred pulse anastomosis can be performed, or a bypass anastomosis between the abdominal stirred pulse, common iliac stirred pulse, and mesenteric membrane superior stirred pulse may be considered. If the tumor invades the inferior vena cava and the involvement is localized, partial venous wall resection can be performed, followed by repair with an autologous internal jugular vein patch. In some cases, resection of the infrahepatic renal vein segment of the inferior vena cava may be necessary, along with right nephrectomy and ligation of the left renal vein root. Left renal function can still be preserved by relying on collateral circulation of the left renal vein. During pheochromocytoma resection, special attention must be paid to controlling blood pressure and replenishing blood volume intraoperatively.

For some primary undifferentiated carcinomas or lymphomas, postoperative radiotherapy may be an option. cervical malignancy with cachexia may be treated with chemotherapy.