Mark R. Anderson, MD, MSc
Judd W. Moul, MD, FACS
BASICS
DESCRIPTION
• Retroperitoneal masses and cysts can originate from retroperitoneal organs or nonorgan tissue. The latter are relatively rare.
• 70–80% of primary retroperitoneal neoplasms are malignant in nature, and these account for 0.1–0.2% of all malignancies in the body.
• Most cystic lesions within the retroperitoneum are benign; unless the lesion is mostly solid then suspect malignancy.
• Metastatic disease is the most common etiology of a solid retroperitoneal mass.
• Liposarcomas are among the most common of primary retroperitoneal tumors and are distinguished by their often large dimensions and range of subtypes.
– Peak incidence: Ages 40–60.
– 10–15% of sarcomas, and approximately 20% of these lesions arise in the retroperitoneum.
– Often recur usually within the 1st 6 mo after surgery.
EPIDEMIOLOGY
Incidence
Retroperitoneal sarcoma: Accounts for <1% of all adult malignancy, or 9,500 new diagnoses per year, ∼2.7 cases per million per year of retroperitoneal sarcoma
Prevalence
N/A
RISK FACTORS
• Primary, solid/cystic retroperitoneal mass: Previous radiotherapy (dose dependant), chemical exposure (vinyl chloride, arsenic), HIV/AIDS
• Primary, cystic retroperitoneal mass: Parasitic infection, embryonic remnants, prior lymphadenectomy
Genetics
• Tuberous sclerosis (TS1, TS2 mutation, tumor suppressor loss)
• Werner syndrome (chromosome 8 alteration, premature aging)
• Li–Fraumeni syndrome (p53 mutation, tumor suppressor loss)
• Neurofibromatosis (NF1, NF2 mutation)
• Liposarcomas are being reclassified based on a molecular basis. Well-differentiated and dedifferentiated lesions are a continuum of lesions based on the genetic abnormality of giant and ring chromosomes usually involving chromosome 12.
• Gene amplification, particularly of MDM2, drives their pathology.
• Myxoid and round-cell lesions are another continuum that have fusion transcripts caused by translocations in chromosomes 16 and 12.
• Alveolar rhabdomyosarcoma t(2;13) (q35;q14) PAX3-FKHR, and t(1;13) (p36;q14) PAX7-FKHR
• Sporadic gastrointestinal stromal tumor activating kinase mutations KIT or PDGFRA
PATHOPHYSIOLOGY
• The retroperitoneum extends from the diaphragm superiorly to the pelvis inferiorly and is situated between the posterior pariet al peritoneum anteriorly and the transversalis fascia posteriorly (1).
• The anterior pararenal space is bordered anteriorly by the posterior pariet al peritoneum, posteriorly by the anterior renal fascia (Gerota fascia), and laterally by the lateroconal fascia.
• The anterior pararenal space is subdivided into the pancreaticoduodenal space (contains the pancreas and duodenum) and the pericolonic space (contains ascending and descending colon).
• The posterior pararenal space is situated between the posterior renal fascia (Zuckerkandl fascia) and the transversalis fascia.
• The perirenal space is located between the anterior renal fascia and the posterior renal fascia.
• The great vessel space is the fat-containing region that surrounds the aorta and the inferior vena cava (IVC) and lies anterior to the vertebral bodies and psoas muscles.
• Below the kidneys, the anterior and posterior pararenal spaces merge to form the infrarenal retroperitoneal space, which communicates inferiorly with the prevesical space and extraperitoneal compartments of the pelvis.
• Due to the loose connective tissue in the retroperitoneum, tumors can have widespread growth and extension before clinical presentation.
ASSOCIATED CONDITIONS
N/A
GENERAL PREVENTION
N/A
DIAGNOSIS
HISTORY
• Headaches, palpitations, etc. for hypertension secondary to pheochromocytoma
• Unexplained weight loss
• Constitutional symptoms
• Night sweats
• History of chemotherapy, radiation therapy
• Back or bone pain
• Medications: Methysergide, methyldopa, LSD
• GI complaints: Nausea, vomiting, pain, constipation, increasing abdominal girth
PHYSICAL EXAM
• Vitals for hypertension
• Cachexia
• Lymphadenopathy
• Neurologic deficits from paraneoplastic syndrome
• Lower-extremity lymphedema
• Breast exam
• Testicular exam
• Abdominal mass
• Signs of virilization
DIAGNOSTIC TESTS & INTERPRETATION
Lab
• CBC: Leukocytosis (infection or lymphoma), leukopenia, anemia
• Serum chemistry: Elevated serum creatinine, azotemia (obstructive uropathy), transaminitis (biliary obstruction), and elevated alkaline phosphatase (bone involvement).
• AFP, LDH, and β-HCG: Testicular tumor markers
• ESR: Elevated in retroperitoneal fibrosis
• Urinalysis: Hematuria, pyuria
• Urine cytology: Evidence of a malignant urothelial source
• Blood and urine culture
• Adrenal mass: Pheochromocytoma screen
– Plasma metanephrines
96–100% sensitivity, 85–89% specificity
– 24-hr urine-fractionated metanephrines
91–98% sensitivity and specificity
Imaging
• Adrenal: CT washout for adenoma, MRI “light bulb” sign/T2 bright for carcinoma and pheochromocytoma, MIBG scan for pheochromocytoma (2)
• CT urogram for RCC and urothelial carcinoma
• CT can show enhancement, fat density, water density to help characterize underlying components
• MRI better at defining local invasion
• Ultrasound can differentiate between solid and fluid-filled masses but not good at determining malignant potential or regional mets.
• CT with contrast has relative contraindication if GFR <60, MRI has relative contraindication if GFR <30.
• MAG-3 diuretic renal scan can determine relative differential function between each kidney and urine obstruction.
• Testicular sonogram for mass
• Bone scan, mammogram if needed
• Cystogram if pelvic lipomatosis
Diagnostic Procedures/Surgery
• Image-guided biopsy: CT- or US-guided fine-needle aspiration is usually feasible, but core-needle biopsy improves diagnostic capability
• Open surgical biopsy: Best option if the mass is small and inconveniently located for needle biopsy
• Be prepared to complete the resection if sarcoma identified
• Aspiration of cyst: Fluid for cytology, culture, creatinine
• Angiogram: To delineate relationship of tumor to vascular anatomy or to determine extent of aneurysm
Pathologic Findings
• Metastasis pathology is consistent with primary tumor pathology.
• Determination of benign vs. malignant tissue is not always possible, leaving final determination to the surgical pathology.
• Well-differentiated liposarcomas mostly resemble lipomas and are typically low grade.
• Pleomorphic liposarcomas comprise 10–15% defined as high-grade malignant variants with very bizarre nuclei and huge lipoblasts and carry poor prognosis.
• Liposarcoma is most common (35%), followed by leiomyosarcoma (30%), malignant fibrous histiocytoma (20%), rhabdomyosarcoma, and peripheral nerve neoplasm.
• Lymphoma: Diffuse, monomorphous proliferation of lymphocytes.
• Fibrosis: Cellular and acellular variants coexist; fibroblast and collagen proliferation.
DIFFERENTIAL DIAGNOSIS
• Solid masses—Benign (malignant variant in parenthesis)
– Lipoma (liposarcoma)
– Leiomyoma (leiomyosarcoma)
– Fibroma (chondro-, synovial cell-, fibrosarcoma)
– Rhabdomyoma (rhabdomyosarcoma)
– Hemangioma (angiosarcoma)
– Perivascular epithelioid cell tumor (PECT): Angiomyolipoma, lymphangioleiomyomatosis, clear cell “sugar” tumor, clear cell myomelanocytic tumor, pigmented melanotic tumor (sarcoma variants)
– Gastrointestinal stromal tumor, aka GIST
– Myxoma (myxosarcoma)
– Chordoma
– Schwannoma, neurofibroma
– Ganglioneuroma, ganglioneuroblastoma (neuroblastoma)
– Paraganglioma, pheochromocytoma (pheochromocytoma)
– Mature teratoma (seminoma, nonseminoma germ cell tumors; choriocarcinoma, malignant teratoma, yolk sac, embryonal, mixed)
– Sex cord: Granulose, thecoma, Sertoli–Leydig (rarely malignant)
– Malignant lymphoma, extramedullary plasmacytoma, fibrous histiocytoma
• Cystic malignant masses
– Mucinous cystadenoma or cystadenocarcinoma
– Mesothelioma
– Cystic teratoma
– Paraganglioma, neurilemmoma, sarcoma
• Cystic nonmalignant mass
– Hematoma
– Urinoma
– Lymphocele
– Pancreatic cyst and pseudocyst
– Lymphangioma
– Postoperative seroma
TREATMENT
GENERAL MEASURES
• Need tissue diagnosis via primary excision or needle biopsy
• Core biopsy better than fine needle if possible
MEDICATION
First Line
• Metastatic lesions and lymphoproliferative cancers are best treated with systemic, tumor-specific chemotherapy (in most cases).
• Sarcomas respond variably to chemotherapy, depending on the histology, and generally do not influence survival.
• Pheochromocytoma needs α-blocking blood pressure control, followed by β-blockade. Some advocate single agent calcium channel blockade.
• May need stress steroids if functional adrenal tumor suppresses contralateral function.
• Infected retroperitoneal cysts are treated with broad-spectrum (gram positive and negative) antibiotics until culture sensitivities are known:
– Ampicillin 1 g IV q6h (gram positive)
– Gentamicin 5–7 mg/kg/d (gram negative)
Second Line
N/A
SURGERY/OTHER PROCEDURES
• Metastatic site resection may be beneficial for prognosis and/or symptoms for RCC and testicular tumors
• Liposarcoma needs primary excision
• Extensive lymph node resection commonly needed in liposarcoma and testicular cancer (modified templates used in some instances)
• Benign cysts can be aspirated and sclerosed
ADDITIONAL TREATMENT
Radiation Therapy
• Retroperitoneal sarcoma is typically radiation resistant.
• Intraoperative radiotherapy for sarcoma has been shown to improve local control rates, but does not improve survival.
Additional Therapies
N/A
Complementary & Alternative Therapies
N/A
ONGOING CARE
PROGNOSIS
• 5- and 10-yr survival following surgical resection of retroperitoneal sarcoma is 45% and 29%.
• Poorly differentiated liposarcoma metastasize.
• Completely resected, nonmetastatic, and low-grade sarcomas are associated with improved survival.
• Leiomyosarcoma is an independent predictor of poor outcome.
• Adrenal carcinoma typically presents late stage and has poor prognosis even with complete resection.
• Pheochromocytoma has good prognosis.
• RCC has good prognosis though is most lethal GU cancer and present with mets ∼25% of time.
COMPLICATIONS
• Bowel injury
• Adjacent organ injury (liver, spleen, pancreas)
• Lymphocele
• Deep vein thrombosis
• Wound infection
• Transfusion-dependent anemia
FOLLOW-UP
Patient Monitoring
Schedule imaging that is intensive during 1st 2 yr (q3–6mo) followed by biannual, migrating to annual by year 5 is generally recommended for most retroperitoneal masses.
Patient Resources
N/A
REFERENCES
1. Osman S, Lehnert BE, Elojeimy S, et al. A comprehensive review of the retroperitoneal anatomy, neoplasms, and pattern of disease spread. Curr Probl Diagn Radiol. 2013;42(5):191–208.
2. Rajiah P, Sinha R, Cuevas C, et al. Imaging of uncommon retroperitoneal mass. Radiographics. 2011;31:949–976.
ADDITIONAL READING
N/A
See Also (Topic, Algorithm, Media)
• Retroperitoneal Abscess
• Retroperitoneal Fibrosis (RPF, Ormond Disease)
• Retroperitoneal Hematoma
• Retroperitoneal Liposarcoma
• Retroperitoneal Lymphoma
• Retroperitoneal Masses, Fluids, and Cysts Image 
• Retroperitoneal Rheumatoid Nodules
• Retroperitoneal Sarcoma
• Retroperitoneum, Fat Necrosis
CODES
ICD9
• 158.0 Malignant neoplasm of retroperitoneum
• 568.89 Other specified disorders of peritoneum
• 789.39 Abdominal or pelvic swelling, mass, or lump, other specified site
ICD10
• C48.0 Malignant neoplasm of retroperitoneum
• K68.9 Other disorders of retroperitoneum
• R19.09 Other intra-abdominal and pelvic swelling, mass and lump
CLINICAL/SURGICAL PEARLS
Most solid retroperitoneal masses are malignant.