Liposarcoma

Overview

Liposarcoma is a malignant tumor that arises in fat cells in deep soft tissue, such as that inside the thigh or in the retroperitoneum. Liposarcoma is a rare type of cancer that bears a resemblance to fat cells when examined under a microscope.

They are typically large bulky tumors, and tend to have multiple smaller satellites that extend beyond the main confines of the tumor.

Liposarcomas, like all sarcomas, are rare.

Symptoms

Patients usually note a deep seated mass in their soft tissue. Only when the tumor is very large do symptoms of pain or functional disturbances occur.

Retroperitoneal tumors may present themselves with signs of weight loss and emaciation and abdominal pain. These tumors may also compress the kidney or ureter leading to kidney failure.

Causes

Scientists do not yet know the cause of liposarcoma. Although patients sometimes notice a tumor after they experience an injury, liposarcoma is not known to be caused by trauma. It is also not known to develop from benign lipomas, which are harmless lumps of fat.

Diagnosis

The diagnosis is established by histologic examination of the tissue, i.e., biopsy or excision. Lipoblasts are often present; these are cells with an abundant clear multi-vacuolated cytoplasm and an eccentric darkly staining nucleus that is indented by the vacuoles.

Subtypes

Several subtypes of liposarcoma exist:

• Well-differentiated liposarcoma, synonymous with atypical lipomatous tumor—the former term is used almost exclusively for lesions in the retroperitoneum, while the latter is used for lesions arising elsewhere
• Dedifferentiated liposarcoma—well-differentiated (high-grade) liposarcoma adjacent to a more poorly differentiated tumor
• Myxoid/round cell liposarcoma.
• Pleomorphic liposarcoma.

Diagnosis and treatment plans should only be made by a sarcoma specialist as liposarcoma is frequently misdiagnosed and treated improperly.

Prognosis

The prognosis varies depending on the site of origin, the type of cancer cell, the tumor size, the depth, and proximity to lymph nodes. Well-differentiated liposarcomas treated with surgery, intra-operative distilled water lavage and radiation have a low recurrence rate (about 10%) and rarely metastasize.

Five-year survival rates vary from 100% to 56% based on histological subtype.

Treatment

Surgery is the treatment for primary liposarcomas that have not yet spread to other organs. In most cases, a surgeon will remove the tumor, along with a wide margin of healthy tissue around the tumor, with the goal of leaving the area free of disease and preventing the tumor from returning. Most tumors of the arms and legs can be successfully removed while sparing the involved limb. Occasionally, in about 5% of cases, an amputation is the best way to completely remove the cancer and restore the patient to a functional life. Complete surgical removal of tumors within the abdomen is difficult, in part because of the difficulty in getting clear margins of normal tissue.

The combination of surgery and radiation therapy has been shown to prevent recurrence at the surgical site in about 85-90% of liposarcoma cases. These results vary depending on the subtype of sarcoma that is involved. Radiation therapy may be used before, during or after surgery to kill tumor cells and reduce the chance of the tumor returning in the same location. Radiation therapy that is given before surgery may be more beneficial, but it can also make it more difficult for surgical wounds to heal.

The role of chemotherapy in the treatment of liposarcoma is not clearly defined, but it may be recommended in certain situations where patients are at high risk of recurrence or already have widespread disease.