CHAPTER 94

Bone and Joint Tumors

Bone Tumors

Bone tumors are growths of abnormal cells in bones.

Bone tumors may be cancerous (malignant) or noncancerous (benign) and may develop within the bone or spread to the bone.

Tumors may cause unexplained, progressively worsening bone pain, swelling, or a tendency to fracture easily.

The diagnosis is sometimes based on the results of an imaging test (such as x-ray, computed tomography, or magnetic resonance imaging) but often requires removing a tissue sample of the tumor or bone for examination under a microscope (biopsy).

Bone tumors may be noncancerous or cancerous. A cancerous tumor may spread to other areas of the body. Also, bone tumors may be primary or metastatic. Primary tumors originate in the bone and may be noncancerous or cancerous. Metastatic tumors are cancerous tumors that originate elsewhere in the body (for example, in the breast or prostate gland) and then spread to bone. In children, most cancerous bone tumors are primary. In adults, most cancerous bone tumors are metastatic. Overall, noncancerous bone tumors are relatively common, but cancerous primary bone tumors are rare, occurring in only about 2,500 people yearly in the United States. This number excludes multiple myeloma, a cancer that affects primarily the marrow inside the bone rather than the hard bone tissue.

Symptoms

A person may sometimes have a painless lump, which may eventually become painful, but often the first symptom is bone pain. The pain can be severe (somewhat like a toothache). Pain may occur when at rest or at night and tends to progressively worsen. Sometimes a tumor, especially if cancerous, weakens a bone, causing it to fracture with little or no stress (pathologic fracture).

Diagnosis

A persistently painful joint or limb should be x-rayed. However, x-rays tend to show only that there is an abnormality suggestive of an abnormal growth or a hole in the bone, often without indicating whether a tumor is noncancerous or cancerous. However, some tumors can be identified as benign by an x-ray. For example, this identification is often possible with Paget’s disease, enchondromas, bone cysts, nonossifying fibromas (fibrous growths that have no bone tissue), and fibrous dysplasia. If an x-ray is not conclusive, computed tomography (CT) and magnetic resonance imaging (MRI) often help determine the exact location and size of the tumor and give additional information as to the nature of the tumor, but these tests usually do not provide a specific diagnosis.

If cancer is suspected or is a reasonable possibility, a biopsy is usually necessary for diagnosis. For many tumors, a sample may be taken by inserting a needle into the tumor and withdrawing some cells (aspiration biopsy); however, because the needle used is very small, sometimes normal cells may be sampled and cancer cells are missed, even when cancer cells are lying right beside the normal cells. A biopsy done with a larger needle (core biopsy) is often necessary so that more tissue can be examined. Sometimes, a surgical procedure called open biopsy is necessary to obtain an adequate sample for diagnosis and can sometimes be done at the same time that surgery is done to treat the tumor.

NONCANCEROUS BONE TUMORS

Osteochondromas: Osteochondromas (osteocartilaginous exostoses), the most common type of noncancerous (benign) bone tumors, are usually recognized in people aged 10 to 20 years. These tumors are growths on the surface of a bone, which protrude as hard lumps. A person may have one or several tumors. The tendency to develop several tumors may run in families.

At some point in their lives, about 10% of people who have more than one osteochondroma (multiple osteochondromatosis) may develop a cancerous (malignant) bone tumor called a chondrosarcoma (presumably formed from an existing osteochondroma). Surgical removal is generally appropriate if one of the tumors enlarges or causes new symptoms (for example, if the tumor disturbs growth of the bone, enlarges, or presses on nearby nerves, muscles, or surrounding structures). Such people should also visit their doctor for regular examinations. However, people who have only one osteochondroma are unlikely to develop a chondrosarcoma; therefore, a single osteochondroma usually does not need to be removed unless it causes symptoms.

Enchondromas: Enchondromas may occur at any age but tend to be recognized in those aged 10 to 40 years. These tumors develop in the central part of a bone. The tumors often are discovered when x-rays are taken for other reasons and often can be diagnosed by their appearance on the x-ray. Some enchondromas may enlarge and cause pain. If an enchondroma does not cause pain and does not appear to be cancerous on x-rays or other imaging tests, it does not have to be removed or treated. However, follow-up x-rays may be taken to monitor its size. If the tumor cannot be identified with certainty on x-rays or if it causes pain, removal of a tissue sample for examination under a microscope (biopsy) may be needed to determine whether it is noncancerous or cancerous.

Chondroblastomas: Chondroblastomas are rare tumors that grow in the ends of bones. They usually occur in people aged 10 to 20 years. These tumors may cause pain, leading to their discovery. If untreated, these tumors may continue to grow and destroy bone and the joint; therefore, treatment consists of surgical removal and use of a bone graft to fill in the defect. Graft material can be bone removed from the person’s own pelvis (autograft), processed bone tissue from another person (allograft), or a synthetic bone substitute. Occasionally, these tumors recur after surgery.

Chondromyxofibromas: Chondromyxofibromas are very rare tumors that occur in people younger than 30. They are usually located off to one side near the ends of the bones in the extremities (the limbs). Pain is the usual symptom. These tumors have a distinctive appearance on x-rays. Treatment consists of surgical removal, which usually provides a cure, although these tumors sometimes recur.

Osteoid Osteomas: Osteoid osteomas are very small tumors that commonly develop in people aged 10 to 35. They are most common in the arms or legs but can occur in any bone. They usually cause pain that worsens at night and is relieved by low doses of aspirin or other nonsteroidal anti-inflammatory drugs (NSAIDs). Sometimes the muscles surrounding the tumor waste away (atrophy). This condition may improve after the tumor is removed. If the tumor develops near the growth plate (the part of the bone from which growth occurs in children), bone growth can be overstimulated. This can cause the limbs to grow to unequal sizes. Bone scans using radioactive tracers help determine the exact location of the tumor. Sometimes the tumor is difficult to locate, and additional tests, such as computed tomography (CT), may be needed.

To treat the tumor permanently, usually a doctor punctures the skin and inserts a needle-like probe into the tumor, using CT as guidance for placement. A radiofrequency pulse is then applied to destroy the tumor. While this is done, the person is under general, spinal, or nerve block anesthesia (see page 2053). The prognosis is good, and pain should resolve. Surgically removing the tumor is another way to eliminate the pain permanently. Alternatively, some people prefer to take pain relievers (analgesics) indefinitely rather than undergo a procedure. The pain may eventually resolve without treatment.

Giant Cell Tumors: Giant cell tumors usually occur in people in their 20s and 30s. These tumors most commonly originate in the ends of bones and may extend into adjacent tissue. They usually cause pain. Treatment depends on the tumor’s size. A tumor can be surgically removed, and the hole can be filled with bone graft or synthetic bone cement to preserve the bone’s structure. Occasionally, very extensive tumors may require removal of the affected segment of bone and reconstruction of the joint. One treatment is a surgical procedure called curettage, in which the tumor is scraped out with a scoop-shaped instrument. After this treatment, about 10% of tumors recur. Giant cell tumors rarely become cancerous.

PRIMARY CANCEROUS BONE TUMORS

Multiple Myeloma: Multiple myeloma (see also page 1051) is the most common primary cancerous (malignant) bone tumor and occurs mostly in older adults. However, it is cancer that involves the bone marrow (the blood-forming tissue inside the cavity of the bone) rather than the hard tissue that makes up the bone. Thus, it is not always considered a primary bone tumor. It is more common than cancers of the hard tissue that makes up bone. Multiple myeloma may affect one or more bones, so pain may occur in one location or in several. If only one bone is involved in only one place, the condition is called a plasmacytoma. If more than one area is involved, the condition is called multiple myeloma. Treatment is complex and may include chemotherapy, radiation therapy, and sometimes surgery.

Osteosarcoma: Osteosarcoma (osteogenic sarcoma) is the second most common type of primary cancerous bone tumor but is less common than multiple myeloma. This cancer causes abnormal bone cells to grow. Although most common among people aged 10 to 25 years, osteosarcomas can occur at any age. Older people who have Paget’s disease (see page 547), have undergone bone radiation, or have areas of dead bone tissue that form from sickle cell anemia and other conditions (bone infarcts) sometimes develop this type of tumor. About half of these tumors occur in or around the knee, but they can originate in any bone. They tend to spread (metastasize) to the lungs. Usually, these tumors cause pain and swelling. X-rays are taken, but removal of a tissue sample for examination under a microscope (biopsy) is needed for diagnosis.

People need a chest x-ray and a computed tomography (CT) scan to detect cancer that has metastasized to the lung and a bone scan to detect cancer that has spread to other bones.

Osteosarcomas are usually treated with a combination of chemotherapy and surgery. Usually, chemotherapy is given first. Pain often subsides during this phase of treatment. Then the tumor is surgically removed without damaging (violating) the tumor, such as by cutting it. Violating the tumor spills its cells, which can cause the cancer to recur in the same area.

About 65% of people who have this type of tumor survive for at least 5 years after diagnosis when chemotherapy is provided and the cancer has not metastasized. If chemotherapy destroys almost all of the cancer, the chance of surviving at least 5 years is greater than 90%. Because surgical procedures have improved, the affected arm or leg can usually be saved and reconstructed. In the past, the affected limb often had to be amputated.

Fibrosarcomas and Malignant Fibrous Histiocytomas: Fibrosarcomas and malignant fibrous histiocytomas affect the same age group as and are similar to osteosarcomas in appearance, location, symptoms, and prognosis. These cancerous tumors have cells that produce cancerous fibrous (connective) tissue rather than cancerous bony tissue. Treatment is similar to that of osteosarcoma.

Chondrosarcomas: Chondrosarcomas are tumors composed of cancerous cartilage cells. These tumors tend to occur in older adults. Many chondrosarcomas are slow-growing or low-grade tumors, meaning that they are less likely to spread than some other tumors. They often can be cured with surgery. However, some chondrosarcomas are high-grade tumors, which tend to metastasize. A biopsy is needed for diagnosis.

Low-grade chondrosarcomas are often removed from the bone by scraping it with a scoop-shaped instrument (curettage) and by using liquid nitrogen, phenol, or an argon beam to kill the surface tumor cells embedded in bone. Other chondrosarcomas must be completely removed surgically without damaging (violating) the tumor, which risks spreading the tumor’s cells. Chondrosarcomas do not respond to chemotherapy or radiation therapy. Amputation of the arm or leg is rarely necessary. More than 75% of people who have a chondrosarcoma survive if the entire tumor is removed.

Ewing’s Sarcoma of Bone: Ewing’s sarcoma is a cancerous tumor that affects males more often than females and appears most commonly in people aged 10 to 25 years. Most of these tumors develop in the arms or legs, but they may develop in any bone. Pain and swelling are the most common symptoms. Tumors may become quite large, sometimes affecting the entire length of a bone. The tumor may include a large mass of soft (non-bone) tissue. Although CT and magnetic resonance imaging (MRI) can help determine the exact size of the tumor, a biopsy is needed for diagnosis. Treatment includes various combinations of surgery, chemotherapy, and radiation therapy, depending on whether surgery is practical or, if attempted, successful. Treatment can cure more than 60% of people who have Ewing’s sarcoma.

Lymphoma of Bone: Lymphoma of bone (previously called reticulum cell sarcoma) is a cancerous tumor that usually affects people in their 40s and 50s. It can originate in any bone or elsewhere in the body and then spread to bone. Usually, this tumor causes pain and swelling and an accumulation of soft tissue. The damaged bone is prone to fractures. Treatment usually consists of a combination of chemotherapy and radiation therapy, which seems to be as effective as amputation or surgical removal of the tumor. Amputation is rarely necessary. If a bone seems to be prone to fracture, doctors may stabilize it surgically in an attempt to prevent fracture.

Malignant Giant Cell Tumors: Malignant giant cell tumors are rare and cancerous and are usually located at the extreme end of a long bone (arm or thigh bone). Treatment is similar to that of osteosarcomas, but the cure rate is low.

Chordomas: Chordomas are rare and cancerous and tend to occur at the ends of the spinal column, usually in the middle of the base of the spine (sacrum) or tailbone or near the base of the skull. A chordoma affecting the sacrum or tailbone causes nearly constant pain. A chordoma in the base of the skull can cause nerve problems, most commonly in those to the eye. Symptoms may exist for months to several years before diagnosis. Chordomas do not usually spread to other bones, but they may recur. Chordomas affecting the sacrum or tailbone may be cured by surgical removal. Chordomas in the base of the skull usually cannot be cured surgically but may respond to radiation therapy.

METASTATIC BONE TUMORS

Cancers, particularly of the breast, lung, prostate gland, kidney, thyroid gland, and colon, may spread to the bone (metastasize).

An imaging test may show the bone abnormality, or a sample of tissue may need to be removed and tested (biopsy).

Radiation therapy, chemotherapy, or surgery may be recommended.

Prostate cancer in males and breast cancer in females are the most common cancers. Lung cancer is the most common cause of cancer death in both sexes. Metastatic bone tumors are cancers that have spread to the bone from their original site elsewhere in the body (see page 1075). Cancers most likely to spread to the bone include those of the breast, lung, prostate gland, kidney, thyroid gland, and colon. However, any cancer may eventually spread to bone. Cancer may spread to any bone, although cancers do not commonly spread to bone below the mid forearm or mid calf. When they do, most often the metastasis will be from lung or sometimes kidney cancer.

Diagnosis

A person who has or has had cancer and develops bone pain or swelling is evaluated for metastatic bone tumors. Bone scans using radioactive tracers and x-rays can help locate these tumors. Magnetic resonance imaging (MRI) or positron emission tomography (PET) is even more accurate. Occasionally, a metastatic bone tumor causes symptoms before the original cancer has been detected. Symptoms may consist of pain or a fracture where the tumor has weakened the bone (a pathologic fracture). In these situations, a biopsy usually gives clues as to the location of the original cancer, because the type of cancer tissue can often be recognized under the microscope and direct the doctor to the primary cancer (for example, lung, breast, prostate, kidney, thyroid, or colon).

Treatment

Treatment depends on the type of cancer that has spread to the bone. Some types respond to chemotherapy, some to radiation therapy, some to both, and some to neither. Radiation therapy is usually most effective. Surgery to stabilize the bone can sometimes prevent fractures. Some metastatic bone lesions require removal of part of a limb and rebuilding of the limb and joint. When the original (primary) cancer has been removed and only a single metastasis in the bone exists (especially when the metastasis develops years after the original tumor), surgical removal with reconstruction, sometimes combined with radiation therapy, chemotherapy, or both, rarely may be curative but may significantly improve the quality of life as well as the function or appearance of the limb.

One of the goals of treatment is to minimize loss of bone tissue. Loss of bone tissue can cause pain and make bones prone to fractures, which can require surgery. Bone loss can be minimized by using radiation therapy and drugs that prevent bone loss (such as bisphosphonates) before bone loss is extensive and pain occurs. If tumors cause the vertebra to collapse but not to put pressure against the spinal cord, kyphoplasty can be used. In vertebroplasty (injection alone) or kyphoplasty (use of an expanding balloon first), bone cement (methyl methacrylate) is injected into the bone to make the area expand, which can relieve pain and prevent further collapse. If the tumors appear to be at risk of collapse that could cause spinal cord damage (such as paraplegia), treatment to decompress the pressure and stabilize the spine may be recommended.

Other Bone Abnormalities

Many noncancerous (benign) bone abnormalities may resemble bone tumors but are not.

Unicameral Bone Cyst: Unicameral bone cysts occur near the parts of the bone from which growth occurs (growth plates) in the arms or legs in children. The cysts often cause nearby bones to thin, which can lead to a fracture. Cysts may heal and may disappear as the fracture heals. Most often, these cysts are treated by injection with corticosteroids, often repeatedly, processed bone putty, or synthetic bone substitutes. Cysts that are more than 2 inches (about 5 centimeters) long or wide, particularly in children, may require surgery to remove the contents of the cyst from the bone by scraping it with a scoop-shaped instrument (curettage) and transplantation of bone from one site to another (bone grafting). However, many people with these cysts respond to injections rather than invasive surgery. Regardless of treatment, the cyst remains or recurs in about 10 to 15% of people.

Fibrous Dysplasia: Fibrous dysplasia involves abnormal bone development during childhood. It may affect one bone or several bones. Birth marks and signs of early puberty (see box on page 1755) may be present; this is also called Albright’s syndrome. The abnormal bone growths commonly stop developing at puberty. This condition rarely becomes cancerous (malignant). Calcitonin injections or bisphosphonates administered intravenously may help relieve the pain. A surgical procedure may correct deformities, fractures that do not heal with casting, or pain that cannot be relieved any other way.

Aneurysmal Bone Cyst: Aneurysmal bone cysts usually develop before people reach age 25, and the cause is not known. These cysts usually occur near the outer ends of the long bones (upper arm and thigh bones), but almost any bone may be affected. The cyst tends to grow slowly. A new bone shell forms around the cyst and is often wider than the original bone. Pain and swelling are common. The cyst may be present for a few weeks to a year before diagnosis.

Surgical removal of the entire cyst is the most successful treatment, but sometimes the cysts recur if they are not removed completely. Radiation should be avoided when possible because cancerous tumors occasionally develop later. However, radiation may be the treatment of choice for cysts that cannot be treated surgically and are compressing the spinal cord.

Joint Tumors

Tumors rarely affect joints unless the joints are near a bone or soft-tissue tumor. However, two conditions—synovial chondromatosis and pigmented villonodular synovitis—occur in the lining (synovium) of joints. These tumors are noncancerous (benign) but aggressive. Both conditions usually affect one joint, most often the knee and then the hip, and can cause pain and an accumulation of fluid. Treatment for both requires surgical removal of the abnormal synovium (synovectomy).

Synovial Chondromatosis: Synovial chondromatosis (previously called synovial osteochondromatosis) is a condition in which cells in the lining of the joint turn into cartilage-producing cells. These converted cells can form clumps of cartilage, which then shed into the space around the joint, forming loose bodies, each of which may be no larger than a grain of rice, and cause pain and swelling. This condition rarely becomes cancerous (malignant). Recurrence is common.

Pigmented Villonodular Synovitis: Pigmented villonodular synovitis causes the lining of the joint to become swollen and grow. This growth harms the cartilage and bone around the joint. The lining also produces extra fluid that can cause pain and swelling. The process often causes bloody fluid to appear in the joint. It usually affects one joint. A total joint replacement may be needed if the condition recurs. On rare occasions after several synovectomies, radiation therapy can be used.