Liposarcoma

Liposarcoma is a malignant tumor that arises in fat cells in deep soft tissue, such as that inside the thigh or in the retroperitoneum.

They are typically large bulky tumors which tend to have multiple smaller satellites extending 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.

Diagnosis
The diagnosis is established by histologic examination of the tissue, i.e. biopsy or excisional biopsy. 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, which consists of well-differentiated liposarcoma adjacent to a more poorly differentiated tumor.
 * Myxoid/round cell liposarcoma.
 * Pleomorphic liposarcoma.

Incidence and prevalence
Most frequent in middle-aged and older adults (age 40 and above), liposarcomas are the second most common of all soft-tissue sarcomas following malignant fibrous histiocytomas. Annually 2.5 cases occur per million population.

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 and radiation have a low recurrence rate (about 10%) and rarely metastasize. Five-year survival rates vary from 100% to 39% based on histological subtype.