Malignant soft tissue tumors are categorized by their behavior to metastasize ranging from low grade to high grade.
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Malignant Soft Tissue Tumors (Sarcomas)
Malignant soft tissue tumors, or soft tissue sarcomas, are more common than bone sarcomas. They usually occur in adults and present as a large painless or painful soft tissue mass. Because benign soft tissue "lumps" are far more common than malignant ones, the diagnosis of a soft tissue sarcoma may be made after excision of a presumed benign mass at a local hospital or in the local doctor's office. When the pathologist reports a sarcoma, the patients are referred to us, a cancer center, for staging studies to assess the local extent and/or spread of the tumor and for further treatment (surgery, chemotherapy or radiation).
Soft tissue tumors are also classified by their tissue type and grade. The higher the grade, the greater the chance for aggressive growth at the original site and for metastases to distant sites. The most common metastatic site is the lungs. Certain sarcomas, such as synovial sarcoma, epithelioid sarcoma and rhabdomyosarcoma (the most common childhood soft tissue sarcoma) may also spread to the lymph nodes.
Staging a soft tissue tumor involves evaluating the histology (tissue grade) of the tumor, how extensive the tumor is at the primary site, and whether or not there are distant metastases. All of these characteristics help describe the tumor's behavior (biologic activity), the patient's prognosis and the best treatment option.
The MRI scan is the best imaging study for soft tissue tumors because of its sensitive technique to show differences between normal and sarcoma tissue. It also clearly shows the relation of the tumor to nearby nerves and blood vessels. A chest CT scan is always necessary to rule out lung metastases, and a biopsy will determine diagnosis and treatment.
Liposarcoma A malignant soft tissue tumor of fat tissue containing malignant lipoblasts. It usually occurs in the thigh, abdomen area (retroperitoneum) and behind the knee (popliteal fossa). The tumor tissue has four types: myxoid (low grade), round cell (high grade), pleomorphic (giant cell-high grade), and well differentiated (low grade). Patients must undergo all staging studies. The MRI scan is more sensitive than the CT scan for this type of sarcoma. The MRI shows high grade liposarcomas to be more vascular and denser than lower grades. Treatment consists of wide excision of the tumor with radiation therapy and sometimes chemotherapy depending on the tumor size and/or presence of lung metastases. Patients with tumors larger than 8 centimeters usually have preoperative chemotherapy and radiation followed by the surgery and postoperative chemotherapy (MAID protocol). Postoperative radiation is only required if the pathology evaluation reveals positive margins (tumor cells present in the surrounding tissue).
Malignant Fibrous Histiocytoma (MFH) A high grade malignant soft tissue tumor of fibrous tissue arranged in a pin wheel pattern along with other bizarre looking cells. It is the most common soft tissue sarcoma in older adults and is more common in men. MFH is usually located in the upper and lower extremities and the abdominal area. MFH can occur as a primary bone tumor as noted in the section on bone tumors. MFH is best imaged with an MRI scan, but chest CT scans must be done to stage the tumor. Treatment for low grade tumors involves wide excision and adjuvant therapy such as radiation. High grade tumors require resections with radical margins with both radiation and chemotherapy recommended. Patients with tumors larger than 8 centimeters will undergo the MAID protocol as discussed with liposarcoma.
Fibrosarcoma A malignant soft tissue tumor or sarcoma that accounts for less than 10% of soft tissue tumors. It occurs more frequently in men, usually in the lower extremities. Tumor tissue looks very similar to malignant fibrous histiocytoma (MFH). In the past, most tumors of muscle and bone (musculoskeletal) were diagnosed as fibrosarcomas. Today, pathologists are able to be more specific with cell classification. Thus, only tumor tissue with spindle cells arranged in a 'herringbone pattern' are called fibrosarcomas. In addition to looking like MFH, high grade fibrosarcomas may resemble synovial sarcoma. Low grade fibrosarcomas have to be distinguished from an aggressive fibromatosis or desmoid-type tumors. The importance of adequate staging studies and proper interpretation of the biopsy to determine diagnosis can not be stressed enough.
Treatment for high grade fibrosarcoma involves a wide excision, usually combined with radiation therapy. Lower grade tumors may not need chemotherapy, but surgical margins must be adequate or else radiation will be required. Patients with tumors larger than 8 centimeters will undergo the MAID protocol as discussed with liposarcoma. Children and adolescents are more likely to be diagnosed with an aggressive benign fibromatosis instead of a low grade fibrosarcoma. They usually do well with excision of the tumor.
Synovial Sarcoma A malignant soft tissue tumor that arises near, but not, as the name implies, in the joint itself. About 10% of soft tissue sarcomas are synovial sarcomas. The patient usually presents with a painful mass next to a joint which is growing in size. It usually occurs in teenagers or patients under 40 years of age, most often in the lower leg around the knee. Lower grade synovial sarcomas tend to be found on the hands or feet, and may be confused with a benign ganglion. X-rays show a soft tissue thick shadow with calcifications (deposits of calcium salts in normal bone or abnormally in soft tissue) in it. A biopsy is necessary to rule out the many other possible soft tissue masses that have calcifications but are benign. Metastases to lymph nodes (small kidney-shaped organs of lymphoid tissue that lie along the lymphatic vessels) are more common with synovial sarcoma than other types of soft tissue sarcomas. The tumor may also spread to the lungs in more advanced cases. Treatment consists of radical or wide excision of the tumor with adjuvant therapy (chemotherapy and/or radiation therapy). Small, low grade tumors may do well with excision only.
Leiomyosarcoma and Rhabdomyosarcoma Malignant soft tissue tumors of muscle. Leiomyosarcoma involves smooth muscle of blood vessels or organ walls and rhabdomyosarcoma involves skeletal muscle. Although they are both tumors of muscle, they have very different characteristics. Leiomyosarcoma is a high grade soft tissue sarcoma that usually penetrates beyond its compartment (stage IIB). It usually occurs in adults, especially women. The most common site is the abdomen (retroperitoneum). Leiomyosarcomas are classified by their location: retroperitoneum, subcutaneous skin, blood vessels or extremities. Treatment is surgical excision with or without radiation, and occasionally chemotherapy.
Rhabdomyosarcoma The most common soft tissue sarcoma in children, occurring more in boys than girls. About 15-20% of all soft tissue sarcomas are rhabdomyosarcomas. Examination of the tumor tissue shows four types: embryonal, boytroid, alveolar and pleomorphic. The location of the tumor is related to the patient's age. Head, neck and pelvis are the most common sites in younger patients. In adolescents, extremity and testicular tumors are the most common because rhabdomyosarcoma has a significant rate of metastases to lymph nodes. Lymph node biopsies are sometimes done.
Treatment for extremity rhabdomyosarcoma involves adjuvant therapy (chemotherapy and/or radiation therapy) and usually wide margin excisions. Leiomyosarcomas involving major nerves and blood vessels may need a resection with reconstruction of the vessels, or an amputation. The local recurrence rate is very high if surgical margins are not adequate.
Angiosarcoma A high grade malignant soft tissue tumor involving blood vessel cells. Hemangioendothelioma and hemangiopericytoma are lower grade tumors. Only 1-2% of soft tissue sarcomas come from vascular origin. Angiosarcomas usually occur in men between the ages of 40 and 70. They are found in the skin, both superficial and deep soft tissue, the breast, liver and bone. The site and extent of the lesion is clearly seen on the MRI or CT scan staging studies. The bone scan shows marked uptake in the tumor area. Prognosis for low grade hemangioendothelioma and hemangiopericytoma is better than high grade angiosarcoma. Treatment for all involves a wide excision. Of course, other adjuvant therapy depends on the grade and stage of the tumor at the time of presentation.
Malignant Schwannoma (Neurofibrosarcoma) A malignant soft tissue tumor involving the nerves. It is also known as neurofibrosarcoma or fibrosarcoma of nerve sheath. The words 'malignant schwannoma' are also used to note that the tumor cells resemble Schwann cells. These tumors may arise within a preexisting benign schwannoma, especially in neurofibromatosis. This changing from benign to malignant is called malignant transformation. Ten percent of all soft tissue sarcomas are malignant schwannomas, and half of them are related to neurofibromatosis (NF or von Recklinghausen's disease). They occur more often in men who present with a large mass causing pain which radiates or travels down the extremity.
Examination of the tumor usually shows the nerve entering at the top of the tumor and existing at the bottom of the tumor. The tumor cells are shaped like commas and collect in a wavy, picket-fence type pattern. Wide excision with limb-sparing procedures or amputation are treatment options for malignant schwannomas, along with radiation and chemotherapy. Patients with tumors larger than 8 centimeters will undergo the MAID protocol as discussed with liposarcoma.