Retroperitoneal liposarcoma is a subtype of liposarcoma and is a malignant tumor of mesenchymal origin that may arise in any fat-containing region of the body. It is one of the most common primary retroperitoneal neoplasms.
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Epidemiology
Most cases occur in patients in the 5th to 7th decades of life, with no gender predilection 4.
Liposarcomas represent the most common variety of malignant retroperitoneal tumor.
Pathology
There are five histological subtypes:
- well-differentiated: ~55%, low grade
- lipoma-like
- inflammatory
- sclerosing
- myxoid: ~30%, low-to-intermediate grade
- pleomorphic: high grade
- round cell: high grade
- dedifferentiated: high grade
Metastatic disease is hematogenous and the extent of metastases is related to the histological grade of the tumor.
Radiographic features
CT
- varying amount of fat and soft tissue
- from purely fat with rare thin septa (usually low-grade lesions) to a very heterogeneous mass with extensive amounts of soft tissue component (usually high-grade lesions)
- multiple septa
- enhancing soft tissue components
MRI
- myxoid type:
- T2: hyperintense myxoid gelatinous components
- T1 C+ (Gd): delayed post-contrast enhancement
Treatment and prognosis
The primary treatment option is resection if possible. However, local recurrence is common and occurs in two-thirds of patients. This is usually a sign of incomplete resection and highlights the difficulty in discriminating liposarcomas from normal retroperitoneal fat.
Differential diagnosis
- retroperitoneal leiomyosarcoma
- retroperitoneal undifferentiated pleomorphic sarcoma (previously known as malignant fibrous histiocytoma MFH)
- retroperitoneal fibrosarcoma
- retroperitoneal lipoma
- extremely rare; therefore, should not be entertained in the differential for retroperitoneal fat-containing lesions 4
- exophytic renal angiomyolipoma (AML)
- presence of a large vessel extending into the renal cortex suggestive of AML; liposarcomas are hypovascular
- claw sign
- renal parenchymal defect at the site of tumor contact strongly favors the diagnosis of exophytic angiomyolipoma
- calcifications suggest liposarcoma 3
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