Liposarcoma

The liposarcoma is a rare malignant tumor of the soft tissue ( sarcoma), which has histological characteristics of adipocytes, or fat cell precursors. With a share of 16-18 %, the liposarcoma is the second most common soft tissue sarcoma after malignant fibrous histiocytoma. The first description of liposarcoma as a disease entity was in 1857 by Rudolf Virchow.

Epidemiology

The incidence of liposarcoma is given internationally with about 2.5 new cases per million population per year. With an average age of onset of 50 years, there is a tumor of the adult who is nevertheless observed rarely in children and young adults. Men are slightly more frequently affected than women. Geographic or ethnic differences in frequency have not yet been reported.

Etiology

The causes of the emergence of a liposarcoma based are largely unknown. Described is a possible relationship to previous injuries and exposure to ionizing radiation. The lipoma, a benign and non- frequent Fettgewebstumor, is not a typical precursor change liposarcoma, but should be able to form its starting point in individual cases according to some authors. Other sources dispute this view and point out that a transition of a lipoma in a liposarcoma previously could never be convincingly documented.

Pathology

From the macroscopic her picture liposarcomas are often relatively well and often even capsule- limited nodular or lobulated, yellowish to gray-white tumors that can reach a considerable size and weight of several kilograms depending on the location. The seemingly good demarcation may have the prove deceptive, as in the vicinity of the primary tumor sometimes smaller tumor metastases are found. Liposarcomas are preferably found in the deep soft tissue of the lower extremity ( 59%), upper extremity (16 %), the retroperitoneum (15% ) and the trunk ( 8%). Particularly common are the affected thigh ( 41%).

By histological (ie tissue) examination can be distinguished several subtypes of liposarcoma, which show a different prognosis and also preferred sometimes occur in certain regions of the body:

The degree of dedifferentiation of liposarcoma indicates how much the tumor tissue differs morphologically from mature adipose tissue. This is therefore significant because with increasing geweblicher immaturity as an increasingly more vicious biological behavior of the tumor and a worse prognosis are to be expected (aggressive local growth, tendency to recurrence, metastasis). Sometimes the terms atypical lipomatous tumor or atypical lipoma For well-differentiated liposarcomas are used because they can be very similar to a lipoma on the one hand morphologically and also in the absence of tumor progression not metastasize, so that they lack a prognostically important feature of malignant tumors. It is now generally accepted that round cell liposarcomas represent a dedifferentiated ( geweblich immature and therefore malicious behaving ) myxoid variant of liposarcoma.

Molecular Pathology

Genetic changes are common, affecting among other things, a region on the long arm of chromosome 12 ( 12q13 -15) with amplification of the MDM2 gene (murine double minute oncogene ) and the coding for the cyclin -dependent kinase 4 CDK4 gene. The concomitant overexpression of the corresponding genes can be detected at the RNA and protein level, and potentially contribute to the demarcation against both benign lipomas and other soft tissue sarcomas.

Clinical symptoms

Liposarcomas are often clinically apparent only in advanced stages as deep-seated, slow-growing tumorous tissue mass. The exact symptoms is determined mainly by the location of the tumor. The tumor growth may be associated general symptoms include fatigue, malaise, weight loss, nausea and vomiting.

Diagnosis

Imaging techniques such as computed tomography, magnetic resonance imaging, angiography or scintigraphy provide diagnostic clues and allow an assessment of the spread of the tumor disease. For definitive diagnosis, a biopsy and histological examination of the tumor tissue obtained by a pathologist is usually required.

Therapy

The most promising therapeutic approach is the complete surgical removal of the tumor while maintaining an adequate safety margin. Additional therapeutic options are the local irradiation and chemotherapy. Although liposarcoma is considered the strahlensensibelste sarcoma, an increase in survival by radiotherapy in scientific studies so far not been convincingly demonstrated. The chemotherapy of liposarcoma has currently still experimental character.

Forecast

The cure rates are in addition to the possibility of complete surgical removal depends on which there is histological subtype of liposarcoma. The well-differentiated myxoid liposarcoma, and most show with a five - year survival rate of 100 or 88 percent of a favorable prognosis. This results in part to the fact that these forms hardly prone to metastasis. In contrast, about 50 percent of patients die with a round cell or poorly differentiated liposarcoma within five years of their malignancy. Metastatic tumor metastases affecting mainly the lungs (20 % ), bone ( 8%), lymph nodes ( 6%) and the liver ( 5%).