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Diagnosing and Staging Soft Tissue Sarcoma

Imaging studies and other tests will help determine the size and location of the tumor and whether any other areas of the body are involved. They will also help determine the prognosis (prediction of outcome for a disease) of a soft tissue sarcoma. In general, masses that are bigger than 5 cm and located deep in the tissues are more likely to be cancerous.

Magnetic resonance imaging (MRI) scan. An MRI can help identify the tumor's size and depth since it clearly shows the tumor's relationship to normal muscle, fat, nerves, and blood vessels. It can also be used to check the tumor's response to treatment and observe the progression of the disease.

(Left) This MRI clearly shows a large, soft tissue sarcoma in the inner thigh. (Right) The same tumor as shown in a cross-section CT scan.

X-rays. X-rays provide images of dense structures such as bone. In the case of soft tissue sarcomas, they can be used to evaluate whether or not the bone is involved with the tumor. They can also show if there is any calcification or bone tissue inside the tumor. X-rays may also help in the diagnosis of certain tumors that may contain calcium deposits such as synovial sarcoma and liposarcoma.

Computerized tomography (CT) scan. Like an x-ray, a CT scan can be used to clearly outline how much bone is involved with a tumor. It is also useful in detecting the spread of the cancer to the lungs, abdomen, and pelvis. A CT scan is sometimes used instead of an MRI for masses that are located around a metal implant.

Biopsy. A biopsy may be necessary to confirm the diagnosis of soft tissue sarcoma. In a biopsy, a tissue sample of the tumor is taken and examined under a microscope. Your doctor may give you a local anesthetic to numb the area and take a sample using a needle. A biopsy can also be performed as a small operation. An MRI is used to guide the biopsy.

Other tests. Bone scans are used to detect the spread of a tumor into a bone or to determine if the tumor has spread to other bones in the body. Positron Emission Tomography (PET) scans may be helpful in monitoring a tumor's response to treatment or in determining if there may be other tumors hidden in the body.

Grading. In addition to identifying the size and depth of the tumor, another important factor in staging the disease is determining the aggressiveness, or grade, of the cancer cells of the soft tissue tumor. Using the tissue specimen taken during a biopsy, the pathologist can identify the type of the cancer, where it came from, and whether it is of high or low grade. The doctor is very careful when taking biopsy samples to avoid the risk of contaminating normal tissue with cancer cells.

Surgery

The extent of the surgery performed depends on several factors, including the amount of tissue that needs to be removed and the functional outcome that is expected afterwards.

Excision. If the sarcoma has not spread, surgery is done to remove the tumor and any surrounding tissues that could potentially be affected by the cancer. Even healthy tissues may need to be removed in order to reduce the chance of the cancer returning.

Advances in reconstructive surgery allow the transfer and repair of skin, blood vessels, and nerves, making it possible to remove more tissue surrounding the tumor yet still preserve a functional limb.

Amputation. In the event that adequate removal of the tumor requires sacrificing important nerves, blood vessels, and muscle structures, amputation may be necessary. Although limb preservation is the goal, if the result is a limb that is numb and not useful, an amputation followed by proper artificial limb fitting could provide improved function and quality of life.

Radiation

Radiation therapy is often combined with surgery to lower the risk of the tumor returning to the same location. Radiation can be administered either before or after the tumor is removed. The timing of the radiation depends upon the tumor site and the doctor's judgment.

Chemotherapy

The role of chemotherapy in treating soft tissue sarcomas is still controversial. At best, there is modest benefit in improving survival through chemotherapy. The chemotherapy drugs that have been most effective against soft tissue sarcomas are doxorubicin (Adriamycin®) and ifosfamide (Ifex®).

Newer drugs that target specific cellular traits are being researched. The first drug to work by this method was imatinib (Gleevac®), which has been effective at treating a specific type of sarcoma—gastrointestinal stromal tumor (GIST). Chemotherapy is mainly used in tumors with a poor outcome—for instance, in large, high-grade tumors that have a high risk of spread to other body sites, particularly when they occur in young people.

Liposarcoma

This tumor is composed of fatty tissue that usually appears as an enlarging, painless mass deep in the muscles of the limbs. It can also occur in the abdomen or buttock, where it can stay undetected for a long period of time and possibly evolve to a more aggressive type. A complete surgical removal of the tumor is needed. It is commonly seen in adult men and women over the age of 50. The course of the disease depends on the type and location of the tumor.

There are several types of liposarcoma. The well differentiated liposarcoma occurs in the limbs and rarely spreads to other organs; it almost never results in death. The more aggressive dedifferentiated type is commonly located in the abdomen or groin and has a higher chance of recurring locally and spreading to distant areas. Another fairly common type is myxoid liposarcoma which, although very rare, occurs in younger patients and is often seen in the deep thigh muscles. The round cell liposarcoma sometimes is seen together with the myxoid type and is prone to recur and spread to other organs.

Fibrosarcoma

This is a malignant tumor made up mostly of cells of fibrous tissues and collagen. Two different clinical behaviors characterize the two main groups of fibrosarcoma. Adult fibrosarcoma occurs in middle-aged to older adults and is commonly seen in the deep soft tissues of the extremities and the trunk. This tumor can be caused by previous treatment with radiation therapy. It can spread to the lungs and bone. The mortality rate can be rather high depending on the aggressiveness (grade) of the tumor cells.

Infantile fibrosarcoma differs from the adult form in many ways. Most cases are congenital (present at birth) and almost never occur after the age of 2 years. It has a better outcome with a lower chance of tumor regrowth and spread.

Myxofibrosarcoma

This is the most common malignant soft tissue tumor in late adulthood. It may be divided into subtypes based on the predominating cells present. The most common location is in the lower limbs, particularly the thigh region, where it can appear as a painless mass. Less frequently, it can grow in the abdomen and be undetected until the patient starts to develop symptoms related to an increase in abdominal pressure, such as bloating, frequent urination, or constipation. There have been some reports of myxofibrosarcoma developing in patients who received high doses of radiation in the past, and other reports suggest a viral or a chemical cause. In most cases, the origin is not known.

Rhabdomyosarcoma

This is the most common malignant soft tissue tumor in children. It occurs most often between the ages of 2 and 6 and 14 and 18. The botryoid and embryonal subtypes can occur earlier in infancy through age 15. The alveolar subtype occurs on average at age 16. The tumor can grow quite large in a short period of time, causing pain, discomfort, or joint stiffness due to pressure on the adjacent soft tissue structures. It is seen mostly in the head and neck region. In 25% of cases, it is found on the trunk and limbs. This tumor is aggressive and difficult to control.

Synovial Sarcoma

These tumors occur deep in the muscle of both the upper and, more frequently, lower limbs. They are common in early adulthood, particularly among young males in their thirties. The mass may remain small for some time but can noticeably enlarge. Sometimes there is a history of trauma preceding the mass. Recent studies show that a genetic abnormality is present in the tumor cells. The risk of spread, mostly to the lungs, can be high and can take as long as 5 to 10 years. This is why a long-term follow-up period is recommended after treatment.

Epithelioid Sarcoma

This rare tumor most often develops in the forearm and hand but may also be seen on the trunk or legs. Patients typically are males in their teens or twenties. The tumor can be deceiving because it can mimic benign (noncancerous) masses in the hand, including small tumors just beneath the skin that may resemble an infection. The source of this tumor is not clear, but a genetic abnormality involving an immature cell type is likely. There is no known hereditary pattern. Risk of recurrence is very high and is usually due to an incomplete removal of the initial lesion. It can spread to the lungs and lymph nodes and affect the likelihood of survival.

Alveolar Soft Part Sarcoma

This rare slowly growing tumor occurs mainly in adolescents and young adults and develops in the deep thigh area in nearly half of cases, although it tends to develop in the head and neck region in younger children. Other organs such as the lungs, bones, and brain may be affected and cause a patient to seek treatment. In some individuals, there appears to be a relationship between pregnancy and the occurrence of alveolar soft part sarcoma. Survival depends on the size of the tumor and the presence of distant spread. However, in contrast to other types of cancers, the metastatic tumors in the lungs may grow very slowly over many years.

Clear Cell Sarcoma

Clear cell sarcoma is a tumor common in young adults between the ages of 20 and 40. It is believed to be caused by a genetic abnormality even though no known hereditary pattern can be identified. It grows just beneath the skin affecting tendons and muscle sheaths of the limbs, particularly in the foot and ankle region. The mass can cause pain and patients sometimes develop lymph node enlargements in the armpits or groin signifying cancer spread. Recurrences and distant spread to the lungs and bone are common and can occur even after 10 years. Long-term follow-up is recommended.

Leiomyosarcoma

Middle-aged and older adults are commonly affected by this tumor, which may arise from blood vessels of the trunk and limbs. It can obstruct blood flow to vital organs such as the liver, kidneys, and pancreas. Jaundice, nausea, abdominal distention, and leg swelling are some possible manifestations. Tumors that are located in the limbs are easier to control than the more common abdominal tumors, which tend to be larger and more difficult to remove. It may spread to the lungs and the liver.

Gastrointestinal Stromal Tumor (GIST)

A rare tumor arising in the abdomen, GIST tends to occur in adults. Tumors may become quite large before being noticed. For this reason, complete surgical removal is difficult to achieve compared with sarcomas in the extremities. The development of drug therapy targeted at specific characteristics of cancer cells in GIST has improved the treatment of this tumor compared with surgical removal alone. The first drug that worked with this method was imatinib (Gleevac®). Other drugs are in development and testing phases.