Benign bone tumors almost never metastasize and are best classified by the matrix which the tumor cells produce such as bone, cartilage, fibrous tissue, fat or blood vessel.
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Benign Bone Tumors Benign bone tumors almost never metastasize and are best classified by the matrix which the tumor cells produce such as bone, cartilage, fibrous tissue, fat or blood vessel. Some of these tumors can be described as 'aggressive' because they may recur locally after removal (resection). It is very important to determine whether a tumor is benign or malignant to avoid over or under treatment of the patient.
Osteoid Osteoma A benign bone tumor that produces bone and is small. The patient presents with a small, painful lesion. Other symptoms include tenderness, swelling and a limp. Pain is sharp, deep, usually worse at night and relieved with aspirin. X-rays have a classic pattern which shows a small round or oval focus called a nidus. These tumors usually occur between the ages of 10-20, rarely over age thirty. They are most commonly located in the tibia and femur, but have occurred in almost every bone. Treatment used to be by excision only. Now, there is a newer, non-invasive procedure called heat ablation which is performed by our radiologists. This procedure involves placing an electrode into the tumor which is heated causing a 'microwave' treatment to the tumor. Patients receive general anesthesia for the procedure, but go home the same day with a bandaid over the probe site. Surgical excision involves a two to four day hospital stay. Incomplete excision or curettages (scraping out) of the lesion may lead to tumor recurrence.
Osteoblastoma Much less common than the osteoid osteoma. It may be confused with a malignant tumor and may behave very aggressively. These tumors occur at any age and can be found in any bone but are most common in the spine and long bones. Symptoms include tenderness, swelling, limited motion if near a joint, and pain (not as severe as the osteoid osteoma). The lesion can be seen on plain x-rays. Treatment consists of curettage (scraping out) of the lesion with bone grafting or an excision (removal) depending on the site and potential functional problems. 'Aggressive' osteoblastomas need closer monitoring to rule out recurrence.
Enchondromas Benign cartilage lesions located centrally within the middle of short, long or flat bones and occur at any age. They are the most common bone tumors of the hand. Patients usually have no symptoms (asymptomatic) unless they have fractured. Plain x-rays show the lesion. If the patient is asymptomatic and there is no deformity or fracture, the lesion can be conservatively managed/observed with x-rays. Otherwise, treatment involves curettage with bone packing taken from the patient's iliac crest hip bone (autologous) or donor bone (allograft). At times it may be difficult to distinguish enchondroma from low grade chondrosarcomas.
Multiple Enchondromatosis (Ollier's and Maffucci's syndromes) Less common than the enchondroma and does occur with increased frequency in families. These lesions are usually found at an early age and range in severity from a mild abnormality to severe deformities of the skeletal system, such as large bony masses on the hand bones or shortening and bowing of the extremities. Treatment is focused on correcting or preventing deformities which includes removing (resecting) these masses or placing metal rods in long bones to stabilize the deformed or fractured bones. These tumors can become malignant but this is not very common. Thus, the patients are carefully observed with follow-up (serial) x-rays throughout their lifetime.
Chondroblastoma A very rare benign tumor and occurs more frequently in males especially during adolescence. Most common sites are the top (proximal) and bottom (distal) of the femur, proximal humerus and proximal tibia. There are growth plates also located in these areas. If left untreated, growth of the involved bones could be interrupted. On x-ray, the lesion is round to oval in shape. Treatment usually requires curettage and packing of the lesion with autologous or allograft bone with careful attention to avoid injury to the growth plates. These tumors have about a 20% chance of recurring after curettage.
Chondromyxoid Fibroma A very rare benign tumor made of fibrous myxoid elements. It may occur at any age, but usually between twenty and thirty. Most common sites are the proximal tibia and distal femur. On x-ray, it looks very unique because it expands the edges (cortex) of the bone into the soft tissues and has a scalloped inner margin. Treatment is either curettage with bone grafting or excision (removal) in suitable locations. These tumors have the highest rate of recurrence (40%) of any benign cartilage lesion. Thus, the patient must be followed closely for several years.
Solitary Osteocartilaginous Exostosis (OCE) or Osteochondroma The most common benign tumor of bone probably caused by a genetic defect in the cartilage of an embryo (unborn child). They occur at the ends of bones at any age. The patient presents with a hard, painless mass fixed on the bone. On x-ray they appear as bony outgrowths of the cortex (side of the bone) projecting away from the joints. Examination of this tumor's tissue shows a cartilage cap which causes its growth, very similar to the growth of a normal bone. These tumors usually do not cause the patient trouble. However, if pain develops or they fracture or interfere with surrounding vessels and nerves, the tumor is removed (excised). Recurrence is unlikely, as is the possibility of the benign tumor turning malignant.
The multiple hereditary form of osteocartilaginous exostosis (HMOCE) is a genetic autosomal dominant problem in which multiple osteochondromas develop. They may distort the skeleton and cause functional problems. Common characteristics include short stature, bowing or knock-knee deformities of the lower legs, forearm or hand deformity, and poor joint function. Treatment focuses on managing these deformities in childhood and monitoring them in adulthood to see if the benign status changes to a malignant one. In these patients there is a very low chance of one of the osteochondromas becoming malignant in adulthood, but this is not common. Onset of pain or sudden growth in tumor size should cause the patient to seek medical attention for further staging studies. Bone scans are helpful in following these lesions in adulthood. Again, treatment consists of excision if the patient has symptoms. Malignant tumors, usually low grade chondrosarcomas, which arise from the previously quiet benign lesions are also excised. Additional treatment such as radiation or chemotherapy is seldom.
Fibrous Cortical Defect and Non-Ossifying Fibroma (NOF) The most common benign bone tumors in children. Both types are located in the shafts of the long bones, especially the distal femur, proximal and distal tibia and also in the upper extremities (proximal humerus, distal radius and ulna). Most of these tumors disappear after adolescence. They usually do not cause symptoms unless a fracture has occurred. Biopsies to confirm diagnosis are usually unnecessary because the tumor appearance on x-ray is so classic. The fibrous cortical defect has a thick bony margin and slight bulging of the edge or side (cortex) of the long bone. By adulthood, the lesions move away from the growth plate and heal. The cause of these lesions is unclear, but may be related to a defect in the growth plate. No metastases have ever been reported. These tumors usually disappear (spontaneous regression). Treatment involves observation with routine x-rays if the diagnosis can be made from the original x-ray. If the diagnosis is in doubt, or if the lesion is likely to weaken the bone and cause a fracture through the lesion, then biopsy and curettage with bone grafting is advised. If a pathologic fracture occurs, it is allowed to heal before surgical treatment because sometimes the lesion will disappear during fracture healing. Non-ossifying fibromas are virtually identical, but larger.
Fibrous Dysplasia A problem of the bone tissue that probably is a developmental abnormality of the bone versus a true tumor. It is not familial or hereditary. Sometimes diagnosis is made during childhood, but it can go unrecognized until adulthood. On x-ray these tumors have a 'ground glass' appearance and can cause thinning of the cortex. The bone may be enlarged and deformed. Some patients sustain fractures through the lesion. With fibrous dysplasia, the normal bone is replaced with masses of fibrous tissue and thin weak bone. A biopsy may be necessary to rule out more aggressive lesions. Treatment involves correction of bony deformities which usually requires curettage and packing of the lesion with possible internal fixation (metal hardware) if the lesion is located near a joint or a body area requiring extra support. this tumor presents a more difficult problem in the proximal femur. These tumors rarely turn malignant.
Unicameral Bone Cysts Occur primarily in children. The cause is unknown but it is thought to be an abnormality of the growth plate or circulation problems of the veins of the bone involved. The cysts are usually found in the proximal humerus of a growing child but may occur in the proximal femur and other bones. In adults, these lesions may be found in the heel (calcaneus) or flat bones. They are usually discovered incidentally or after a fracture through the cyst. The cyst is clearly outlined on an x-ray. The bone is widened and the cortex is thin. The cavity of the cyst is filled with a serum-like fluid. Treatment is by needle aspiration of the cyst with steroid injection or bone marrow and demineralized bone matrix (Grafton®) injection. This is a day surgery procedure under general anesthesia with a success rate of about 80%, but it may require three or more injections to make the cyst heal. Curettage and packing with bone graft is the more invasive procedure requiring a surgical incision and a few days in the hospital. Malignancy arising from a cyst almost never happens.
Aneurysmal Bone Cyst A benign bone lesion of unknown cause. It may occur alone or with other types of benign bone lesions. They usually are located in the long bones and spine in patients less than twenty years old. Typical complaints are swelling and pain which usually follows an injury. X-rays show a clearly outlined, bulging, destructive and eccentric lesion of the bone. The cyst tissue is made of spongy spaces filled with unclotted blood. It is important for these cysts to be distinguished from malignant bone tumors so biopsy is usually required. Treatment is by curettage with bone grafting or resection depending on the location of the cyst. The recurrence rate after currettage approaches 30% and this is one of the reasons for excision when the tumor involves an expendable bone.
Benign Vascular Tumors of Bone Very rare type of tumor. The benign hemangioma of bone is usually solitary (found only in one bone) but can affect more than one bone. Hemangiomas are found in the spine, skull, long bones and pelvis. Local pain, swelling and pathologic fracture (fracture through the bone tumor) may occur. Isolated spine lesions (tumors) usually do not cause symptoms. On x-ray, the lesions appear as lytic defects (destroyed bone). Hemangioma tissue appears as a honey combed pattern made of a conglomeration of vessels. Treatment is usually observation, but may involve resection or curettage when possible. Radiation is given for painful lesions and those located in difficult areas inaccessible to surgery.
Histiocytosis of Bone or Eosinophilic Granuloma (EG) A benign disorder of bone involving usually no more than two or three bony sites of children and young adults. Local pain or fracture are the most common presenting symptoms. Destructive-looking lesions are seen on x-ray. Many lesions will disappear if left alone. A biopsy is usually necessary to establish the diagnosis of EG. If the bony defect is large, curettage with bone grafting is sometimes done. Steroid injections have also been successful to treat these bony lesions. There are variations of histiocytosis with more organ involvement and more generalized disease with endocrine abnormalities. Treatment options may include radiation therapy to relieve symptoms, curettage or chemotherapy to treat systemic disease.
Giant Cell Tumor (GCT) A benign tumor of bone but has the potential to be locally aggressive, meaning that it may recur in the same bone or the soft tissue where the original tumor was excised. The cause of this tumor is unknown. It occurs most often between the ages of 20-40 years. GCT is usually located around the knee, either the distal femur or proximal tibia. The distal radius, proximal humerus, distal tibia and sacrum are other common sites. Unlike other benign lesions, GCT can metastasize to a distant site such as the lungs, but this is rare.
Patients present with a deep, persistent pain in the area of tumor. The rate of the tumor's growth seems to be accelerated during pregnancy because of the increase in hormones. A pathologic fracture may occur, as well as adjacent joint effusions (fluid in the joint). On x-ray, there is thinning and expansion of the cortex, erosion and possible cortex perforation and associated soft tissue mass. The giant cell tumor tissue is very vascular.
Treatment consists of curettage with cement packing. Local recurrences occur in a low percentage of patients, so close follow-up is mandatory. If the tumor is located in the proximal fibula, a resection is done. A wide resection with allograft reconstruction is the treatment of choice for very large, poorly defined tumors with soft tissue mass or pathologic fracture. Although rare, giant cell tumors can spread to the lungs. Thus, a chest x-ray must always be done at follow-up visits in addition to an x-ray of the body part to rule out distant metastases and local recurrence. Treatment for the rare lung metastases involves chemotherapy and resection of the lung nodules.