Liposarcoma is a malignant tumor of adipose tissue. It can affect any part of the body, but is more often localized in the proximal parts of the lower extremities, in the retroperitoneal tissue or in the shoulder area. It is a single node of irregular shape with uneven density. When bones germinate and nerves are squeezed, it causes sharp pains. It can provoke thrombosis, paresis, paralysis, edema and ischemia of the limb. In advanced cases, fever, exhaustion, anemia and symptoms of general intoxication occur. The diagnosis is made on the basis of examination, MRI, biopsy and other studies. Treatment – surgery, radiotherapy, chemotherapy.
General information
Liposarcoma is a malignant neoplasm from the group of mesenchymal tumors. It develops from lipoblasts (young fat cells), usually located in the intermuscular space, less often in subcutaneous fat. Liposarcoma is the second most common malignant soft tissue tumor after fibrosarcoma. It is very rarely diagnosed in children. The frequency of development increases with age and reaches a maximum by the age of 50-60. Women suffer less often than men. There is no endemicity.
The level of malignancy varies depending on the degree of differentiation of liposarcoma. Highly differentiated tumors grow slowly and proceed relatively favorably. Low-grade forms of liposarcoma are characterized by rapid growth, hematogenic (in 35-40% of cases) and lymphogenic (in 6-9% of cases) metastasis. Relapses occur in 45-75% of patients. Treatment is carried out by specialists in the field of oncology, orthopedics, neurology and phlebology.
Causes
The etiology of the disease has not yet been definitively clarified. It has been established that liposarcoma can develop from lipoma, but such cases are extremely rare. Sometimes malignant tumors of adipose tissue occur near neurofibromas, which suggests that there is a certain connection between liposarcoma and neurofibromatosis. Many researchers indicate mechanical injuries, radiation exposure or contact with carcinogenic substances as risk factors.
Liposarcoma is a single node or diffuse infiltrate of irregular shape. It occurs more often in the intermuscular space, less often it is formed in subcutaneous fat. It is usually located in the proximal parts of the lower extremities. The second place in prevalence is occupied by retroperitoneal liposarcomas, followed in descending order by tumors of the inguinal region, gluteal region and knee joints. Very rarely, the mammary gland, head, neck, the area of the spermatic cord, feet, hands and labia majora are affected. As a rule, the neoplasm is single, multiple liposarcomas are less common.
The surface of the tumor is yellowish or white with a grayish tinge. The section shows a grayish-pink semi-translucent fabric with characteristic areas of “fish meat”. Microscopic examination of liposarcoma reveals both mature fat cells and atypical lipoblasts with stellate or fusiform nuclei. The cellular cytoplasm contains fat inclusions that are detected when stained with Sudan.
Classification
Taking into account the features of the structure and clinical course , the following types of liposarcoma are distinguished:
- Highly differentiated liposarcoma. It is characterized by slow growth. It does not metastasize. The structure resembles a lipoma.
- Sclerosing highly differentiated liposarcoma. It consists of clusters of mature fat cells separated by fibrous layers in which atypical cells are located.
- Inflammatory highly differentiated liposarcoma. The structure resembles one of the previous types of tumors, but differs from them by the presence of pronounced lymphoplasmocytic infiltration.
- Myxoid liposarcoma. It often recurs, is not prone to metastasis. Contains mature fat cells, round and fusiform lipoblasts. It has a mucoid stroma with a large number of small vessels. Sometimes areas with a lower level of cell differentiation are detected in the neoplasm tissue, which is considered as a prognostically unfavorable option.
- Round-cell liposarcoma. It is a low-grade variant of a myxoid tumor. Microscopic examination of the neoplasm reveals areas of primitive round cells. The number of vessels in such areas is less than in areas with a high level of cell differentiation.
- Pleomorphic liposarcoma. It contains giant pleomorphic lipoblasts and a small number of small fusiform or rounded lipoblasts.
- Undifferentiated liposarcoma. It consists of areas with a high degree of differentiation and areas of low-differentiated cells resembling pleomorphic fibrosarcoma or malignant fibrous histiocytoma.
Symptoms
Highly differentiated liposarcomas usually proceed asymptomatically and become an accidental finding when a local deformation occurs or an examination is carried out in connection with other diseases and injuries. The initial stages of low-differentiated liposarcomas are also characterized by an asymptomatic course. Subsequently, clinical manifestations are determined by the lesion of nearby anatomical structures. When nerves are compressed, intense pain occurs, sensitivity disorders, paresis and paralysis are possible.
Vascular compression is complicated by edema and impaired nutrition of the limb. With compression of the venous trunks, phlebitis and deep vein thrombosis can develop. With compression of the arteries, ischemia of the limb is observed. Bone damage in liposarcoma is detected very rarely, accompanied by the development of pain syndrome. With the progression of the process, symptoms of general intoxication, fever, exhaustion and anemia occur. In some cases, liposarcoma metastasizes to the lungs, liver, kidneys, heart, ovaries and bone marrow. Metastases to the lymph nodes are detected very rarely.
On palpation, a soft-elastic or dense tumor of irregular shape with uneven contours is determined. The diameter of the node can reach 20 centimeters. Some neoplasms have a lobular structure. At the initial stages, the liposarcoma shifts in the transverse direction, when the bone germinates, the node becomes stationary. Usually, the tumor is quite clearly delimited from the surrounding tissues, which in combination with expansive growth creates the impression of benign neoplasm. At the same time, liposarcoma actually spreads through the intermuscular spaces.
Diagnostics
The diagnosis is established on the basis of anamnesis, complaints, external examination data and the results of instrumental studies. An MRI of the affected segment is performed, a biopsy is performed, followed by a histological examination of the sample. To exclude metastases, a patient with liposarcoma is referred for ultrasound of internal organs, chest x-ray, radiography and scanning of limb bones. When large vessels are affected, angiography is performed.
The final diagnosis is made taking into account the results of morphological examination. Liposarcoma is differentiated with lipoma, rhabdomyoma, intramuscular myxoma, myxoid chondrosarcoma, myxoid malignant fibrous histiocytoma, pleomorphic malignant fibrous histiocytoma, lymphoma, neuroblastoma, Ewing’s extraosseous sarcoma, ovarian cell carcinoma and some other malignant neoplasms of soft tissues.
Treatment and prognosis
The treatment is surgical. Perform a wide excision of the tumor with the surrounding unchanged tissues. The liposarcoma is removed together with the muscle group between which the neoplasm is located. In case of a tumor that is poorly delimited from the surrounding tissues and spreads through the intermuscular spaces, amputation or exarticulation of the limb is performed. In the postoperative period, radiation therapy is prescribed. In addition, radiotherapy is used for distant metastases and local relapses. With large fast-growing liposarcomas and tumor metastasis, surgery and radiation therapy are supplemented with chemotherapy.
Local relapses are detected in 45-75% of patients. The probability of recurrence is determined by the localization and type of liposarcoma. Highly differentiated tumors of subcutaneous adipose tissue do not recur. When the same neoplasms are located in the intermuscular spaces, relapses occur in 29% of cases, when localized in retroperitoneal tissue – in 37% of cases. Recurrence is most rarely observed in myxoid liposarcomas. In most cases, recurrent tumors are less differentiated compared to primary ones.
Distant metastasis is detected in 15-45% of cases. Most often, round–cell liposarcomas metastasize, then, in descending order, pleomorphic, myxoid and highly differentiated liposarcomas. Life expectancy is determined by the type and localization of the neoplasm. Myxoid and highly differentiated liposarcomas are considered the most favorable. The five-year survival rate for such tumors ranges from 45 to 65%. Complete recovery is observed in 30-40% of cases. In children, the prognosis is more favorable, in childhood, the five-year survival rate for liposarcoma is 80-90%.