Home > Encyclopedia of Nursing & Allied Health > Sarcomas

Definition

A sarcoma is a malignant tumor (neoplasm), or cancer. Certain sarcomas characteristically spread throughout the body. The word "sarcoma" has its etiology in a Greek word whose definition is "fleshy." Tumors come from the mesenchymal tissue, from which connective tissues, blood, lymphatics, bone, and cartilage come. The blood carries sarcomas throughout the body into neighboring tissue, or via the bloodstream. Frequent sites of extension of the tumors are the lung, the liver, and the brain.

Description

When the original site of the cancer is the bone, there is a primary bone cancer. The tumor originates in or near a bone. Most primary bone tumors are benign, and the cells that compose them do not metastasize (spread) to nearby tissue or to other parts of the body.

Sarcomas account for fewer than 1% of all cancers diagnosed in the United States. They can infiltrate nearby tissues, enter the bloodstream, and metastasize to other bones, tissues, and organs far from the site of the original malignancy. Malignant primary bone tumors are characterized as either:

• cancers that originate in the hard material of the bone
• soft-tissue sarcomas that begin in blood vessels, nerves, or tissues containing muscles, fat, or fiber

Types of bone tumors

Osteogenic sarcoma, or osteosarcoma, is the most common form of primary bone cancer, accounting for about 5% of all cancers in children. Every year, 900 new cases of osteosarcoma are diagnosed in the United States. The disease usually affects teenagers and young adults, and is almost twice as common in males as in females.

Osteosarcomas grow very rapidly. Although they can develop in any bone, but they are most often seen along the edge or on the end of one of the fast-growing long bones that support the arms and legs. Approximately 80% of all osteosarcomas develop in the distal femur or in the proximal tibia (parts of the upper and lower leg nearest the knee). The next likely location for an osteosarcoma is the proximal humerus (the bone of the upper arm closest to the shoulder).

Ewing's sarcoma is the second most common form of childhood bone cancer. Accounting for less than 5% of bone tumors in children, Ewing's sarcoma usually begins in the soft tissue or nerves. It rapidly metastasizes to the lungs, and may metastasize to bones in other parts of the body.

Ewing's sarcoma occurs most frequently in children aged 11–15. It is more often diagnosed in taller teens. Slightly more males than females develop common bone cancer—but this type is the most frequently found carcinoma in children. The disease is rarely diagnosed in children younger than five and adults older than 30. It primarily affects Caucasians, and rarely occurs in African Americans and native Chinese persons.

Chondrosarcomas are cancerous bone tumors that most often appear in middle age. Usually originating in cartilage in ribs, leg, or hip bones, chondrosarcomas grow slowly. They rarely metastasize to the lungs. It takes years for a chondrosarcoma to metastasize to other parts of the body, and some of these tumors never spread.

Parosteal osteogenic sarcomas, fibrosarcomas, and chordomas are rare. Parosteal osteosarcomas generally involve both the bone and the periosteum, the membrane that covers bones. Fibrosarcomas originate in the ends of the bones in the arm or leg, and then spread to soft tissue. Chordomas develop on the skull or spinal cord.

Osteochondromas, which usually develop between persons aged 10–20 years, are the most common noncancerous primary bone tumors. Giant cell tumors generally develop in a section of the femur near the knee. Giant cell tumors are originally benign, but sometimes become malignant.

Causes and symptoms

The cause of bone cancer is unknown, but the tendency to develop it may be inherited. Children who develop bone tumors are often tall for their age, and the disease seems to be associated with growth spurts during childhood and adolescence. Injuries can make the presence of tumors more apparent, but do not cause them.

A bone that has been broken or exposed to high doses of radiation that has been used to treat other cancers is more likely than other bones to develop osteosarcoma. It should be noted, however, that the amount of radiation in diagnostic x rays poses little or no danger of bone cancer development. A history of noncancerous bone disease also increases bone cancer risk.

Cancer of the eye (retinoblastoma) is a rare tumor of the eye that develops in the cells of the retina, and occurs mostly in patients under five years of age. It is known to be hereditary—the condition is an autosomal-dominant trait.

Both benign and malignant bone tumors can distort and weaken bone, causing pain, but benign tumors are generally painless and asymptomatic.

Patients may feel a lump or mass, but pain in the affected area is the most common early symptom of bone cancer. Pain is not constant in the initial stages of the disease; it is aggravated by activity and may be worst at night. If the tumor is located on a leg bone, the patient may limp. Swelling and weakness of the limb may not be noticed until weeks after the pain began.

Other symptoms of bone cancer include:

• a bone that breaks with minimal trauma, also known as a pathologic fracture
• difficulty moving the affected part of the body
• fatigue
• fever
• a lump or swelling on the trunk, an arm or leg, or another bone
• persistent, unexplained back pain
• weight loss

Diagnosis

Physical examination and routine x rays may provide enough evidence to diagnose benign bone tumors, but biopsy (removal of tumor tissue for microscopic analysis) is the only definitive way to determine the nature of the tumor.

A needle biopsy involves using a fine, thin needle to remove small bits of tumor, or a thick needle to extract tissue samples from the innermost part (the core) of the growth. An excisional biopsy is the surgical removal of a small, accessible tumor and a margin of surrounding normal tissue. An incisional biopsy is performed on tumors too large or inaccessible to be completely removed. A portion of the tumor is removed by the surgeon performing an incisional biopsy. Performed under local or general anesthesia, biopsy reveals whether a tumor is benign or malignant, and ideally identifies the type of cancer cells the malignant tumor contains.

Primary bone cancer is usually diagnosed about three months after symptoms first appear. Twenty percent of these malignant tumors will have already metastasized to the lungs or to other parts of the body.

Imaging techniques

The following procedures are used, in conjunction with biopsy, to diagnose bone cancer:

• Plain x rays. These x rays usually provide a clear image of osteosarcomas.
• The computerized tomography (CAT) scan, or computed tomographic scanning (CT), is a specialized x ray that uses a rotating beam to obtain detailed information about an abnormality and its physical relationship to other parts of the body.
• A CAT scan can show differentiation between osteosarcomas and other types of bone tumors, reveal if tumor cells have spread to other tissues, and help surgeons decide which portion of a growth is best to biopsy. Since malignant bone tumors frequently metastasize to the lungs, a CAT scan of the chest should also be performed. The CAT scan can provide information about other organs that may have been affected. Chest and abdominal CAT scans are used to determine whether Ewing's sarcoma has spread to the lungs, liver, or lymph nodes.
• Magnetic resonance imaging (MRI) is a specialized scan that relies on radio waves and powerful magnets to reflect energy patterns created by tissue abnormalities and specific diseases. MRI provides more detailed information than a CAT scan about tumors and marrow cavities of the bone, and can sometimes detect clusters of cancerous cells that have separated from the original tumor. This valuable information helps physicians select the best approach for treatment.
• Radionuclide bone scans involve the injection of a small amount of radioactive material into a vein. Primary tumors, or cells that have metastasized, absorb the radioactive material and present as dark spots on the scan.

Cytogenic and molecular genetic studies, which assess the structure and composition of chromosomes and genes, may also be used to diagnose osteosarcoma. These tests sometimes help to determine the most appropriate form of treatment.

Laboratory studies

A complete blood count (CBC) reveals abnormalities in the blood, and may indicate whether bone marrow has been affected. A blood test that measures levels of the enzyme lactate dehydrogenase (LDH), can be used determine the prognosis for the survival of a given patient.

Immunohistochemistry involves adding special antibodies and chemicals, or stains, to tumor samples. This technique effectively helps the pathologist to identify cells that are found in Ewing's sarcoma, but that are not present in other malignant tumors.

Reverse transcription polymerase chain reaction (RTPCR) relies on chemical analysis of RNA (the substance in the body that transmits genetic information) to:

• Evaluate the effectiveness of cancer therapies.
• Identify mutations consistent with the presence of Ewing's sarcoma.
• Reveal cancer that recurs after treatment has been completed.

Staging

Once bone cancer has been diagnosed, the tumor is staged. This process indicates how far the tumor has spread from its original location. The stage of a tumor helps the oncologist decide which form of treatment is indicated, and to predict how the condition will probably respond to therapy.

An osteosarcoma may be localized or metastatic. A localized osteosarcoma has not spread beyond the bone where it, originated, or beyond nearby muscles, tendons, and other tissues. Metastatic osteosarcoma has spread to the lungs, to bones not directly connected to the bone, or to other tissues or organs.

Treatment

Since the 1960s, when amputation was the only treatment for bone cancer, chemotherapy and innovative surgical techniques have improved survival with intact limbs. Because osteosarcoma is rare, treatment is most often sought at a cancer center staffed by specialists familiar with the disease. A treatment plan for bone cancer, which is devised after the tumor has been diagnosed and staged, may include:

• Radiation therapy. Radiation therapy is used often to treat Ewing's sarcoma.
• Surgery. Surgery, coordinated with diagnostic biopsy, enhances the probability that limb-salvage surgery can be used to remove the cancer, while preserving nearby blood vessels and bones. A metal rod or bone graft is used to replace the area of bone removed. Subsequent surgery may be needed to repair or replace rods that have become loose or broken. Patients who have undergone limb salvage surgery require intensive rehabilitation. It may take as long as one year for a patient to regain full use of a leg following limb salvage surgery. Some patients who undergo this procedure eventually require amputation.
• Chemotherapy. In addition to surgery, chemotherapy is usually administered to kill cancer cells that have separated from the original tumor and spread to other parts of the body. Although chemotherapy can increase the likelihood of future development of another form of cancer, the American Cancer Society maintains that the benefit of chemotherapeutic bone cancer treatment is much greater than its potential risk.
• Amputation. Amputation may be the only therapeutic option for large tumors involving nerves or blood vessels that have not responded to chemotherapy. MRI scans demonstrate the extent of disease in the limb, providing information about how much of it must be removed. The treatment, surgery, is designed to create a cuff (formed of muscles and skin) around the amputated bone. Following surgery, a prosthetic (artificial) leg is fitted over the cuff. Patients who actively participate in the rehabilitation may be walking independently as soon as three months after the amputation.
• Rotationoplasty. Rotationoplasty, sometimes performed after a leg amputation, involves attaching the lower leg and foot to the femur, so that the ankle replaces the knee. A prosthetic is later added to make the leg as long as it is normally. Prosthetic devices are not used to lengthen limbs that remain functional after amputation to remove osteosarcomas located on the upper arm. When an osteosarcoma develops in the jaw bone, the entire lower jaw is removed. Bones from other parts of the body are later grafted onto remaining bone to create a new jaw.

Follow-up treatments

After a patient completes the final course of chemotherapy, a number of tests—CAT or CT scans, bone scans, x rays, and other diagnostic tests—may be repeated to determine if any traces of tumor remain. If none are found, treatment is discontinued, but patients are advised to see their oncologists and orthopedic surgeons every two or three months for the subsequent year. X rays of the chest and affected bone are taken every four months. An annual echocardiogram is recommended to determine whether there have been any adverse cardiovascular effects of chemotherapy, and CT scans are performed every six months.

Patients who have received treatment for Ewing's sarcoma are examined regularly—at gradually lengthening intervals—after completing therapy. Accurate growth measurements are taken at each visit and blood is drawn to test for side effects of treatment. X rays, CAT or CT scans, bone scans, and/or other imaging studies are generally performed every three months during the first year. If no evidence of tumor growth or recurrence is revealed, these tests are performed less frequently in the following years.

Some benign bone tumors shrink or disappear without treatment. However, regular examinations are recommended to determine whether these tumors have changed in any way.

Alternative treatment

Alternative treatments should never be substituted for conventional anticancer treatments or used without the approval of a physician. Some alternative treatments may be used as adjunctive and supportive therapies during and following conventional treatments.

Many patients find that alternative and complementary therapies help to reduce the stress associated with illness, improve immune function and feel better. While there is no evidence that these therapies specifically combat disease, activities such as biofeedback, relaxation, therapeutic touch, massage therapy, and guided imagery have been reported to enhance well-being.

Some cancer patients find that acupuncture alleviates pain, nausea, and vomiting. It may also be effective in helping to maintain energy and relative wellness during surgery, chemotherapy, and radiation. Massage, reflexology, and relaxation techniques are reported to relieve pain, tension, anxiety, and depression.

Claims of effectiveness in fighting cancer have been made for a variety of herbal medicines. These botanical remedies should only be used when prescribed by a practitioner familiar with cancer treatment.

Prognosis

Benign bone tumors rarely recur, but sarcomas can reappear, even after treatment considered effective in eliminating all the cancerous cells.

Likelihood of long-term survival depends on:

• the type and location of the tumor
• how much the tumor has metastasized, and the organs, bones, or tissues affected

More than 85% of patients survive for more than five years after complete surgical removal of low-grade osteosarcomas (tumors that arise in mature tissue and contain a small number of cancerous cells). About 25–30% of patients diagnosed with high-grade osteosarcomas (tumors that develop in immature tissue and contain a large number of cancer cells) will die of the disease.

Two-thirds of all children diagnosed with Ewing's sarcoma live for more than five years after the disease is detected. The outlook is most favorable for children under age 10, and least favorable in patients whose cancer is not diagnosed until after it has metastasized: fewer than three of every 10 of these patients remain alive five years later. More than 80% of patients whose Ewing's sarcoma is confined to a small area, and surgically removed live for at least five years. Postsurgical radiation and chemotherapy add years to their lives. More than 70% of patients live five years or more with a small Ewing's sarcoma that cannot be removed, but only three out of five patients with large, unremovable tumors survive that long. Patients with tumors that do not respond to treatment and those who suffer recurrences have poor outlooks for long-term survival.

Health care team roles

Like other cancer patients, patients with sarcoma are usually cared for by a multidisciplinary team of health professionals. The patient's family physician or primary care provider collaborates with other physician specialists, such as surgeons and oncologists. Radiologic technicians perform x ray, CT, and MRI scans; nurses and laboratory technicians may obtain samples of blood, urine and other laboratory tests.

Before and after any surgical procedures, including biopsies, the procedures may be explained by nurses or physicians, who are also called upon to help prepare patients and families. Depending on the tumor location and treatment plan, patients may also benefit from rehabilitation therapy with physical therapists, nutritional counseling from dietitians, and counseling from social workers or other mental health professionals.

Prevention

Since the causes of most sarcomas are not known, there are no formal recommendations about how to prevent their development. Among families with an inherited tendency to develop soft tissue sarcomas, careful monitoring may help to ensure early diagnosis and treatment of the disease.

In 1999 and 2000, there were a number of studies that reported both genetic and biologic factors in sarcomas. The reports generated by these studies provide evidence that more and more sarcomas possess the same chromosome abnormalities. The reports also point to the high complexity of these genetic changes; which further complicate identifying any single abnormality associated with sarcomas. Despite their limitations, continuing stud ies can yield new, therapeutic treatment modalities. These approaches will be experimental, yet they will facilitate advancement in this arena toward even better disease management.

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KEY TERMS

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Biofeedback—The technique of making unconscious or involuntary bodily processes (as heartbeat or brain waves) perceptible to the senses in order to manipulate them by conscious mental control.

CAT scan (CT scan)—Computerized axial tomography, or computed tomography, tomographic scanning; a specialized x ray that uses a rotating beam to obtain detailed information about an abnormality and its physical relationship to other parts of the body.

Chondrosarcoma—A malignant tumor derived from cartilage cells or their precursors.

Chordoma—Malignant tumor composed of remnants of the embryonic notochord—a flexible rod of cells that in the embryos of higher vertebrates forms the supporting axis of the body—and is found along the spine, attacking especially the bones at the base of the skull, or near the coccyx.

Echocardiogram (ECHO)—The use of beeps of ultrasonic waves directed through the chest wall to record the position and motion of the heart walls or internal structures of the heart.

Ewing's sarcoma—A tumor that invades the shaft of a long bone and that tends to recur, but metastasizes infrequently.

Fibrosarcoma—A sarcoma of relatively low malignancy, consisting mostly of spindle-shaped cells that generally form collagenous fibers of connective tissue.

Magnetic resonance imaging (MRI)—A specialized scan that uses radio waves and powerful magnets to reflect energy created by abnormal tissue and specific diseases.

Metastasis—Transfer of disease from one organ of the body to another not directly connected with it, as a result of transfer of pathogenic microorganisms or to transfer of cells.

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Barbara Wexler