bubble_chart Overview

Retroperitoneal tumors can be divided into benign and malignant types. According to foreign reports, malignant tumors account for about 80%, while domestically it is 56%. Due to the deep location of the tumor and some room for expansion, there are no symptoms in the initial stage, making early diagnosis somewhat difficult. Symptoms only appear when the tumor grows larger, compresses, or invades surrounding organs and tissues, adding difficulty to complete treatment.

bubble_chart Pathological Changes

Retroperitoneal tumors mainly originate from the adipose tissue, loose connective tissue, fascia, muscles, blood vessels, nerve tissue, lymphatic tissue, and embryonic remnants in the retroperitoneal space. Two-thirds are malignant tumors.

1. Benign tumors

Lipoma, fibroma, ganglioneuroma, cystic teratoma, and chemodectoma.

2. Malignant tumors

Lymphosarcoma, liposarcoma, fibrosarcoma, malignant schwannoma, and malignant teratoma.

Common tumors in the retroperitoneal space classified by their tissue origin.

Table Classification of primary retroperitoneal tumors

Tissue origin	Benign	Malignant
From mesoderm
Adipose tissue	Lipoma	Liposarcoma
Smooth muscle	Leiomyoma	Leiomyosarcoma
Connective tissue	Fibroma	Fibrosarcoma
Striated muscle	Rhabdomyoma	Rhabdomyosarcoma
Lymphatic vessels	Lymphangioma	Lymphangiosarcoma
Lymphatic tissue	Lymphoma	Lymphosarcoma, reticulosarcoma, Hodgkin's disease
Blood vessels	Hemangioma, Hemangiopericytoma	Endothelial fleshy tumor, perivascular fleshy tumor
Mesenchymal tissue	Mesenchymoma	Mesenchymal fleshy tumor
From nerves, nerve sheath	Schwannoma, neurofibroma	Malignant schwannoma, neurofibrous fleshy tumor
Sympathetic nerves	Ganglioneuroma	Neuroblastoma, ganglioneuroblastoma
Chromaffin tissue	Pheochromocytoma	Malignant pheochromocytoma
Chemoreceptor	Non-chromaffin paraganglioma (retroperitoneal tumor)	Malignant non-chromaffin paraganglioma
From urogenital ridge	Cyst	Seminoma, choriocarcinoma
From embryonic tissue remnants	Teratoma, dermoid cyst	Malignant teratoma
	Chordoma, embryonic remnant serous cyst	Malignant chordoma
Unknown origin, unclassified	Cyst	Undifferentiated carcinoma, undifferentiated fleshy tumor, undifferentiated malignant tumor, mucinous cystadenocarcinoma, multilocular mucinous cystadenoma with partial malignant transformation

bubble_chart Clinical Manifestations

Retroperitoneal tumors originate from various tissues and are diverse in type and manifestation. These tumors can occur in people of any ethnicity and at any age, with about 10% of cases occurring in children under 10 years old, and approximately 80% exhibiting malignant characteristics. Retroperitoneal tumors generally develop slowly, and except for lymphomas and neuroblastomas, they tend to involve adjacent organs and metastasize late, leading to delayed detection of vague, nonspecific symptoms. The common symptoms and signs are summarized as follows:

I. Symptoms

1. Abdominal Mass Early-stage tumors often present no symptoms and are usually discovered incidentally during physical examinations. Discomfort or pain in the abdomen or back is relatively common. Most patients initially experience abdominal discomfort, with significant abdominal pain appearing in the advanced stage. A minority may report back pain, groin pain, or even pain radiating to the scrotum or knee. As the tumor grows, corresponding symptoms may arise, such as bloating in the upper abdomen (sometimes affecting breathing) or a dragging sensation in the lower abdomen. Slowly growing tumors are better tolerated, with milder symptoms, whereas rapidly enlarging tumors with hemorrhage or necrosis may cause distending pain or severe pain.

2. Compression Symptoms Symptoms caused by compression of adjacent organs include: - Gastric irritation leading to nausea and vomiting. - Rectal compression resulting in increased bowel movements or chronic intestinal obstruction. - Bladder irritation causing frequent and urgent urination. - Ureteral obstruction leading to hydronephrosis. - Invasion of the celiac plexus causing back pain, perineal pain, or lower limb pain. - Compression of veins or lymphatic vessels causing lower limb edema.

3. Systemic Symptoms In advanced malignant tumors, systemic symptoms such as weight loss, fever, fatigue, loss of appetite, or even cachexia may appear. If the tumor is a pheochromocytoma, it may secrete adrenaline and noradrenaline, leading to paroxysmal hypertension. Compression of the pancreas may stimulate insulin secretion, resulting in hypoglycemia.

II. Signs

A palpable mass may be detected in the corresponding abdominal region, with its size and consistency closely related to the duration and nature of the tumor. Retroperitoneal masses are often immobile. Cystic masses may feel fluctuant upon palpation. Benign tumors exhibit fewer and milder signs, whereas malignant tumors present with more signs and grow rapidly, possibly accompanied by tenderness, ascites, lower limb edema, or abdominal varicose veins. Compression of the biliary tract may cause jaundice, while compression of the gastrointestinal tract may lead to chronic incomplete intestinal obstruction.

bubble_chart Auxiliary Examination

1. X-ray Examination Conventional X-ray examination is still often the first choice, but it usually only provides indirect, incomplete, or imprecise images. Plain films may show dense shadows for tumors, while lighter shadows could indicate lipomas or fatty fleshy tumors. Uneven density might suggest dermoid cysts. When tumors necrose to form abscesses or fistulas, gas or gas-fluid levels may occasionally be seen. Calcifications can be observed in hemangiomas, ganglioneuromas, ganglioneuroblastomas, teratomas, dermoid cysts, neurofibromas, schwannomas, chordomas, leiomyomas, or certain metastatic tumors. X-ray plain films of chordomas, neurogenic tumors, or teratomas may sometimes reveal bone destruction or deformation. Pyelography and digestive tract contrast examinations often provide diagnostic reference for retroperitoneal tumors affecting the urinary or digestive tracts.

2. Cavography and Counterflow of Liver Qi Selective stirred pulse angiography can be diagnostically significant for retroperitoneal tumors. Retroperitoneal pneumography has reference value for diagnosing adrenal tumors, though it is now less commonly used.

3. B-mode Ultrasound Examination B-mode ultrasound can also detect retroperitoneal tumors and enlarged lymph nodes, but intestinal gas interference makes precise diagnosis difficult. However, it is relatively reliable for diagnosing or ruling out abdominal aortic stirred pulse aneurysms. Ultrasound-guided biopsy or monitoring post-chemotherapy tumor changes is highly informative. Standalone ultrasound often struggles to differentiate retroperitoneal tumors from abscesses or hematomas. Cystic tumors may be confused with parasitic cysts, inflammatory or traumatic hematomas. Percutaneous fine-needle aspiration biopsy guided by B-mode ultrasound or CT is highly significant for diagnosis, with a confirmation rate of around 80%.

4. CT CT is crucial for diagnosing retroperitoneal tumors, providing information on tumor location, extent, and impact on adjacent tissues. It can also indicate central cystic degeneration (e.g., in leiomyomatous fleshy tumors) and sometimes suggest specific histological diagnoses (e.g., fatty fleshy tumors, lipomas). Additionally, it can detect normal and abnormal retroperitoneal lymph nodes.

5. For Suspected Pheochromocytoma A 24-hour urine test for Black Catechu phenols and their metabolite vanillyl Bitter Apricot Seed acid (VEA) should be performed.

bubble_chart Diagnosis

Based on age, tumor growth rate, signs, and special examinations, the nature of the tumor can be preliminarily assessed. However, surgical exploration and biopsy are required for a definitive diagnosis.

bubble_chart Treatment Measures

Except for lymphoma, surgical resection should be performed. However, due to vague symptoms and late onset, early diagnosis is difficult, and the diagnosis of seasonal disease is often delayed, making surgery challenging with a high mortality rate. Lymphoma can be treated with radiotherapy or chemotherapy, which shows good short-term efficacy. Neuroblastoma in children can also be treated with radiotherapy. Most other retroperitoneal tumors respond poorly to radiotherapy, but it still has some effect in alleviating symptoms such as pain, reducing tumor size, and prolonging life. Therefore, radiotherapy is generally recommended for inoperable cases. Recently, rapidly developing immunotherapy has shown limited efficacy when used alone.

Surgical resection is the primary treatment for retroperitoneal tumors. Due to the complex anatomical relationships in the retroperitoneal space, tumors are often large and frequently invade adjacent organs and tissues, limiting the possibility of complete resection.

I. Surgical Principles

1. Given the diverse origins, numerous types, and complex anatomy of retroperitoneal tumors, thorough preoperative preparation is essential.

2. Complete and thorough resection should be pursued to reduce recurrence rates.

3. For cases with adjacent organ involvement or postoperative recurrence, combined resection of the tumor and affected organs may be performed. One reported case involved a patient with recurrent liposarcoma who underwent a third surgery combining tumor resection with removal of the left kidney, spleen, left colon, and part of the small intestine, remaining recurrence-free for 9 years.

4. If the tumor invades surrounding organs or major blood vessels, making ideal resection impossible, palliative resection or debulking surgery may be considered.

5. Postoperative adjuvant therapies such as chemotherapy, radiotherapy, and/or immunotherapy should be administered for malignant tumors.

II. Factors Affecting Tumor Resectability

The main factors are tumor invasion of major blood vessels, extensive infiltration, peritoneal seeding, and distant metastasis. However, invasion of adjacent organs is not an absolute contraindication for resection. The complete resection rate for retroperitoneal malignancies is reported in foreign literature as 38–70%, while domestic data show a 51% complete resection rate. The 5-year survival rate is 56%, and the 10-year survival rate is 30%. For partially resected or biopsy-only cases, the 5-year survival rate is 8%. Jaques reported that in the complete resection group, 83% underwent combined tumor and organ resection to achieve radical treatment, resulting in a 5-year survival rate of 74%.