Soft tissue sarcoma

soft tissue sarcomaSoft tissue sarcoma is a rare malignant tumor derived from mesenchymal tissue.

 

Description

Soft tissue sarcoma is a group of different malignant tumors, derived from  mesenchymal tissue, which form the body’s soft tissues. Soft tissues include the fat, muscles, tendons, ligaments, skin, fascia, fibrous tissues, blood and lymph vessels, and  nerves. So these tumors may be found anywhere in the body.

 

Incidence

The onset of the disease takes place at the age of 50-55. 50% of tumors originate in the limbs, 40% – in the trunk and retroperitoneum, 10% – in the head and neck.

 

Causes and risk factors

These tumors are more likely to occur in adults older than 50 years. The median age when diagnosis is made is 50-55 years.

Some of the tumors are associated with various hereditary diseases such as familial adenomatous polyposis (FAP), Gardner syndrome, Werner syndrome, basal cell nevus syndrome, tuberous sclerosis, retinoblastoma, neurofibromatosis type 1 (von Recklinghausen disease, NF1) and Li-Fraumeni syndrome .

Exposure to vinyl chloride, arsenic, thorotrast, phenoxyherbicides, chlorophenols and dioxin, radiation therapy and human herpesvirus 8 in anamnesis increase the risk of development of soft tissue sarcoma.

HIV infection is known to cause Kaposi sarcoma, a type of soft tissue sarcomas derived from the blood vessels.

See also: Fibrosarcoma

Subtypes

The most common subtype of soft tissue tumor is malignant fibrous histiocytoma. It accounts for about 40% of all these tumors. The second most common tumor is liposarcoma (25%).

  • Fibroblastic/myofibroblastic tumors include deep and superficial fibromatoses (benign), fibrosarcoma, low-grade myxofibrosarcoma, fibromyxoid sarcoma and sclerosing epithelioid fibrosarcoma;
  • Fibrohistiocytic tumors – undifferentiated pleomorphic sarcoma (pleomorphic, giant cell, highgrade myxofibrosarcoma and inflammatory forms);
  • Adipocytic tumors (atypical lipoma and liposarcoma);
  • Smooth muscle sarcomas (leiomyosarcoma, epithelioid leiomyosarcoma);
  • Skeletal muscle sarcomas (embryonal, alveolar and pleomorphic rhabdomyosarcoma);
  • Vascular sarcomas (epithelioid hemangioendothelioma, deep angiosarcoma, lymphangiosarcoma, Kaposi sarcoma);
  • Neural tumors (neurofibrosarcoma, primitive neuroectodermal tumor);
  • Chondro-osseous tumors (extraskeletal chondro- and osteosarcoma);
  • Paraganglionic tumors (malignant paraganglioma);
  • Others (synovial sarcoma, epithelioid sarcoma, alveolar soft part sarcoma, clear cell sarcoma of soft tissue, extraskeletal myxoid chondrosarcoma, extraskeletal Ewing tumor, undifferentiated sarcoma).

 

Symptoms

The symptoms of sarcoma vary widely according to the location of the lesion.

  • The common symptom of the tumor is a palpable painless mass/lump, which grows gradually. Later the tumor may compress the nearby tissues, nerves and muscles, causing pain.
  • Some of the tumors may limit the mobility of the body, especially when the tumor affects the extremities.
  • If the tumor is superficial erythema and warmth over its surface may occur, as well as the ulceration.
  • The involvement of the bone leads to its fragility and pathological fractures.
  • The sarcoma of the neck is known to cause odynophagia (pain while swallowing), obstruction of the pharynx and airways.
  • A head tumor may cause nasal obstruction and the dysfunction of cranial nerves.
  • Anorexia, abdominal pain, intestinal obstruction, nausea and vomiting are characteristic for abdominal sarcoma.
  • Angiosarcoma appears as purple, bruise-like lesions that tends to bleeding.

In 10% of cases the metastases are already present when the diagnosis is made. Though lymph node metastases are not typical, they may occur due to epithelioid sarcoma, clear cell sarcoma, angiosarcoma and rhabdomyomasarcoma. The lungs, liver and bones are common metastases sites.

 

Diagnosis

Sarcomas of the extremities, head and the neck are usually detected earlier than other sarcomas due to their location.

To evaluate the diagnosis the following tests are required:

  • CT/MRI of a suspicious site;
  • X-ray examination;
  • Incisional, core needle or excisional biopsy of the lesion to evaluate the diagnosis and assess the grade of the tumor;
  • Genetic analysis is performed to detect the mutations associated with soft tissue sarcoma;

 

Treatment

Wide surgical removal of the tumor is the main treatment of sarcoma. Sometimes amputation may be needed.

Pre or postoperative radiotherapy is required for deep tumors or tumors larger than 5 cm in diameter. The radiotherapy dose varies from 40 up to 70 Gy depending on the stage of the tumor.

 

Applicable medications

Adjuvant chemotherapy is required for the treatment of advanced stage sarcoma and metastatic disease. The following protocols are used:

  • Doxorubicin 60–75 mg/m 2  intravenously every 3 weeks, or
  • Doxorubicin 60–75 mg/m 2  intravenously + ifosfamide (5–9 g/ m 2) every 3 weeks;
  • Pazopanib 800 mg per os twice a day;
  • Gemcitabine 1000 mg/ m 2  intravenously;
  • Gemcitabine 900 mg/ m 2  + docetaxel 100 mg/ m 2 every 3 weeks;
  • Trabectedin 1.5 mg/ m 2  (24hour  infusion), every 3 weeks

 

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