Retroperitoneal liposarcoma

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Retroperitoneal liposarcoma is a subtype of liposarcoma and is a malignant tumour of mesenchymal origin that may arise in any fat-containing region of the body. It is one of the most common primary retroperitoneal neoplasms.

Epidemiology

Most cases occur in patients at the 5^th-7^th decades of life, with no gender predilection ⁴.

Liposarcomas represent the most common variety of malignant retroperitoneal tumour.

Pathology

Histology

There are five histological types:

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 haematogenous and the extent of metastases is related to the histological grade of the tumour.

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
- 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 tumour contact strongly favours the diagnosis of exophytic angiomyolipoma
- calcifications suggest liposarcoma ³

~~-<a title="Myxoid liposarcoma" href="/articles/myxoid-liposarcoma">myxoid</a>: ~30%, low-to-intermediate grade</li>~~
+<a href="/articles/myxoid-liposarcoma">myxoid</a>: ~30%, low-to-intermediate grade</li>
~~-<a title="Pleomorphic liposarcoma" href="/articles/pleomorphic-liposarcoma">pleomorphic</a>: high grade</li>~~
+<a href="/articles/pleomorphic-liposarcoma">pleomorphic</a>: high grade</li>
~~-<a title="Dedifferentiated liposarcoma" href="/articles/dedifferentiated-liposarcoma">dedifferentiated</a>: high grade</li>~~
+<a href="/articles/dedifferentiated-liposarcoma">dedifferentiated</a>: high grade</li>

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