TYPES OF BONE TUMORS
The Term "Bone Cancer" or "Bone Tumor"
BONE TUMOR CLASSIFICATIONS
These two terms are very general terms. Bone tumor refers to any abnormal growth from the bone or in the bone, benign or malignant. Bone cancer refers to a malignant bone tumor. It can be a primary malignant tumor like an osteosarcoma, Ewing's sarcoma or chondrosarcoma. It can also be a metastatic carcinoma such as a breast cancer, lung cancer, prostate cancer, kidney cancer and thyroid cancer. It is important to differentiate between the various types of cancers that affect the bone because each has its own type of treatment and prognosis.
Differences between Sarcomas and Carcinomas
Sarcomas and carcinomas are types of malignant tumors that can affect bones. They are derived from different types of cells. Sarcomas are derived from mesodermal (mesenchymal cells) and carcinomas are derived from epithelial types of cells. Sarcomas and carcinomas grow and spread differently. Sarcomas grow like "ball-like" masses and tend to push adjacent structures like arteries, nerves, veins away. They compress adjacent muscles into a pseudocapsule that contains microscopic projections of the tumor referred to as satellite nodules. The local growth of sarcomas like a ball enables resection in most instances. Sarcomas tend to arise primarily (directly) from bone as opposed to spreading to bone from another site. Sarcomas spread most commonly to the lungs. They can also spread to other bones (ie. arise from a bone and spread to other bones) and to the liver. These are the most common sites of spread. Sarcomas rarely spread to lymph nodes. Carcinomas grow in an infiltrative manner and grow through infiltration or invasion of adjacent structures. They more easily invade adjacent nerves, blood vessels and muscles. They do not form a pseudocapsular layer and therefore it is difficult to determine its exact anatomic extent during surgery. This makes it more difficult to remove entirely with surgery. Carcinomas spread to lymph nodes, lungs, bones and many other organs depending on the type of carcinoma. Carcinomas involve bone secondarily, that is by spreading from another site such as the breast to the bone. A patient can have the primary site removed and treated (ie. the breast cancer removed) and years later develop a bone tumor/metastasis from the old breast cancer.
The human body is made up of various organ systems such as the musculoskeletal system (bones and muscles), respiratory system (lungs), cardiovascular system (heart and blood vessels), gastrointestinal system, integumentary system (skin), nervous system (brain, spinal cord and nerves), urinary system (kidneys, bladder). Each system is made up of individual organs that function together to make the system work. Each organ is made up of tissues such as muscle, nerves, connective tissue, bone, epithelial tissue. Tissues combine to make organs. Each individual tissue is made up of specific types of cells. The cell is the smallest building block of the body. The body is made up of billions of cells. The cell contains genetic material in its nucleus (the brain of the cell) that determines the function and characteristics of the cell and therefore of the body and person. The genetic material tells the cell when to grow, divide and replicate. As cells age, they eventually die and are replaced by other cells that divide to replenish the aging cells. Occasionally, an alteration occurs in a cell's genetic material or some other alteration occurs in the cell and the cell begins to grow, divide and replicate itself, uncontrollably. The body's immune system may detect this and destroy the abnormal cells. If the body does not detect this abnormality, then the cell continues to divide and form a tumor.
What is a tumor?
A tumor refers to an abnormal growth in the body. Tumors are made up of abnormal cells that are uncontrollably dividing and replicating themselves. Tumors can be classified as benign or malignant (cancerous). Depending upon the type of cell that the tumor is derived from, a malignant tumor can be classified as a sarcoma or a carcinoma. Malignant tumors can also be considered primary or secondary. In terms of bone tumors, a primary bone tumor arises directly from a particular bone. Secondary bone tumors are tumors that involve the bone but have traveled from a cancer in another part of the body. Primary malignant bone tumors are sarcomas. Secondary bone tumors are called metastatic bone tumors or metastatic bone cancers and most are carcinomas that have traveled from other primary tumors such as breast cancer, lung cancer, prostate cancer, kidney cancer, thyroid cancer and gastrointestinal cancer. For instance, breast cancer that spreads to the bone; the breast cancer is the primary cancer and the breast cancer that is in the bone is a secondary cancer or a metastatic cancer.
What is the difference between benign and malignant tumors?
Benign tumors are not considered cancers. They do not have the ability to spread throughout the body. They generally cause problems or destruction in the bone that they arise from. Benign tumors can also cause additional problems if they grow near critical organs. When they arise from the bone they can cause extensive destruction of the bone. Malignant tumors are cancers. Malignant tumors have the ability to spread throughout the rest of the body. For instance, a malignant bone tumor can spread (metastasize) to the lungs. The tumor in the lung looks exactly like the bone tumor under a microscope. The patient is not considered to have lung cancer but to have a metastatic bone cancer. Likewise, a breast cancer can spread to bone. The patient is not considered to have bone cancer but to have metastatic breast cancer. Malignant tumors also cause destruction in the bone or adjacent tissue that they arise from, in addition to spreading throughout the body.
A sarcoma is a specific type of malignant tumor. It is derived from a particular type of cell referred to as a pluripotential mesenchymal cell. Under normal situations, mesenchymal cells in the body form the bones, muscles, cartilage, connective tissue, blood vessels, blood cells, and nerves. Pluripotential means that the cell has the ability to differentiate or grow along different pathways and form these various types of tissues. Under cancerous conditions, the mesenchymal cells that form a sarcoma can grow along a specific pathway and form tissue that looks like bone, cartilage, muscle, connective tissue, blood vessels. Thus, you can have a bone sarcoma (malignant tumor of bone made up of mesenchymal cells) that is actually producing bone. The name given to this type of tumor is osteosarcoma (osteo means bone; thus osteosarcoma is a bone forming sarcoma). A patient can have a malignant bone tumor that produces cartilage. This is called a chondrosarcoma (chondro means cartilage). Malignant tumors that arise directly from bone are called sarcomas. Sarcoma is greek for "fleshy" or "fish-flesh". The name was given to these types of tumors because of their appearance. They have a fleshy appearance when cut open and examined. Carcinomas are distinctly different from sarcomas. They are derived from cells that look like epithelial cells or glandular cells. These cells do not form bone, muscle, nerve, etc. They do not have this ability. If a carcinoma is growing from a bone, it has usually come from a primary cancer in another part of the body. It is always considered cancerous and malignant because it has spread from another body part or another cancer. Breast cancer, lung cancer, kidney cancer, prostate cancer, thyroid cancer and gastrointestinal cancer are the most common carcinomas that travel or metastasize to bone. They can result in extensive destruction of the bone and can cause the bone to break/fracture. In some areas such as the pelvis and scapula, they can form large tumors that can involve the major nerves and blood vessels to the extremities. This is a serious situation. It can lead to uncontrollable pain and death of the arm or extremity. The tumor in the bone is the same type of tumor as the primary carcinoma. For instance, if breast cancer has spread to the bone, the tumor in the bone is exactly the same as the breast cancer under the microscope. This is considered metastatic breast cancer to the bone. Sarcomas are rare cancers and constitute about 1% of all cancers. Carcinomas are much more common and make up the majority of the remaining cancers that occur yearly.
Primary Bone tumors and sarcomas are rare types of tumors. Bone sarcomas constitute about 1% of all types of cancers that occur in the United States each year. The most common type of bone sarcoma is an osteosarcoma, of which, approximately 600 occur in the United States each year. Bone sarcomas can affect all age groups and particular types have a predilection for specific age groups. For instance, osteosarcoma and Ewing's sarcoma typically occur during the teenage years or early 20s. Chondrosarcoma affects older adults. Overall, there is no strong sex predilection. For the most part, they occur equally as common in males and females, except for a few certain types of bone sarcomas or bone tumors.
What causes tumors?
In reality, nobody knows what causes a sarcoma or a benign bone tumor. Because of the rarity of these tumors it has been difficult to perform extensive research on these types of tumors. Some tumors are related to genetic alterations that can actually be identified with special laboratory tests. There are also some rare genetic syndromes such as neurofibromatosis in which patients are predisposed to sarcomas. Radiation, a commonly employed treatment for certain cancers, can also cause bone sarcomas. Bone sarcomas can arise in the presence of Paget's disease. Certain chemicals have been loosely linked to sarcomas. There are predisposing factors for some carcinomas, such as cigarette smoking and lung cancer. There is a familial or genetic link for breast cancer as well as it being linked to the female sex. (males have breast tissue also).
What is tumor "grade?"
Sarcomas are graded by pathologists. When the pathologist views a biopsy specimen or the final tumor under the microscope, he assigns a grade to the tumor. The grade is based on particular characteristics of the cells that compose the tumor. The grade reflects the degree of malignancy of the sarcoma. The degree of malignancy reflects the potential for the tumor to come back locally (local recurrence) and spread to other parts (metastasize). Sarcomas can be divided into low, intermediate, and high grade tumors. Low grade tumors grow slowly and have very little chance of spreading to other areas of the body. High grade tumors grow rapidly and have a high likelihood of spreading to other body parts, particularly the lungs. Usually, high grade sarcomas have already spread microscopically to other parts of the body by the time the tumor is noticed by the patient. The behavior of intermediate grade tumors falls somewhere in between low and high grade tumors. The grade of the tumor helps determine the type of treatment. Higher grade tumors are generally treated with more aggressive surgery. High grade tumors respond to chemotherapy and low grade tumors do not respond to chemotherapy. High grade tumors tend to respond better to radiation in comparison to low grade tumors. Thus chemotherapy is usually only used for treating high grade tumors with rare exceptions.
How does chemotherapy work?
Chemotherapy is the administration of certain toxic drugs in an attempt to kill cancer cells and cure patients of their cancer, shrink tumors to facilitate surgical resection or prolong a patient's life. Chemotherapy is typically administered for high grade bone sarcomas. It is usually given before surgery (preoperative chemotherapy=neoadjuvant chemotherapy=induction chemotherapy) to try to kill the tumor before taking it out. The terms induction chemotherapy and neoadjuvant chemotherapy refer to giving the chemotherapy before surgery. Giving chemotherapy before surgery makes it easier to remove the tumor and makes it less likely for the tumor to come back in the area where it was removed. At the same time, any microscopic tumor cells that have spread throughout the body are killed. Certain tumors may shrink dramatically following chemotherapy which makes the surgery easier. Less normal tissue is removed. Preoperative chemotherapy also permits us to examine the response that the tumor had to the chemotherapy which helps us estimate the patient's prognosis (it helps us estimate the response of the microscopic tumor cells that have already spread). Preoperative or induction chemotherapy is largely responsible for our present day ability to save 90%-95% of limbs with high grade sarcomas instead of performing amputations. Amputations for high grade bone sarcomas are rarely performed nowadays.
For high grade bone sarcomas, chemotherapy is also usually given postoperatively. When it is given postoperatively, it is referred to as adjuvant chemotherapy. The same chemotherapy agents are used before and after surgery. The purpose of chemotherapy is to kill any tumor cells that have spread throughout the body that can grow and kill the patient. By killing or eradicating these cells, the patient can be cured of the cancer. The entire chemotherapy regimen may require 6 months to 12 months to complete. Some chemotherapy agents require a hospital admission for a few days in order to administer the medications. The following chemotherapy drugs may be used in the treatment of sarcomas: Adriamycin (doxorubicin), ifosfamide, cisplatin, high dose methotrexate, cyclophosphamide, vincristine, actinomycin-D, etoposide. There are complications that are specific to each type of medication. These complications should be thoroughly discussed with the medical oncologist. Some of the general complications or side effects include: hair loss, nausea and vomiting, mucositis, myelosuppression/decrease in the blood counts (neutropenia=drop in white blood cells; anemia=drop in red blood cells; thrombocytopenia=drop in platelets), cardiac dysfunction, hearing loss, kidney failure, neuropathy. Many of these side effects and complications can be minimized with specific medications. Prior to initiating chemotherapy several blood tests will be ordered along with a hearing test and an echocardiogram (asseses the function of the heart). Blood tests will be required frequently throughout the course of the chemotherapy regimen to follow kidney function and blood counts. A special intravenous line will be placed (port-a-cath or groshong) that can stay in place for prolonged periods. This line is directed into the large veins that empty into the cardiopulmonary circulation. It is necessary to place these lines so the chemotherapy can be administered directly into the large veins. Infusion of chemotherapy agents into small veins causes destruction of the small veins. Additionally some agents may spill under the skin and cause skin damage. The patient and family members must be aware that these ports can get infected when the patient's white blood cell count drops. Any fever that develops during chemotherapy must be reported to the oncologist, the patient will be admitted, cultures of the blood obtained along with a chest X-ray and urinalysis to check for bacteria. The patient will be started immediately on intravenous antibiotics. If a line gets infected postoperatively in a patient who has had a prosthetic replacement, the line should be removed. Bacteria can live for long periods on the part of the line that is in the venous sytem. Intravenous antibiotics may not eradiacte the bacteria and the bacteria can spread to the prosthesis and cause a severe limb threatening infection that requires additional surgery and is difficult to cure without removing the prosthesis (impossible to cure with intravenous antibiotics alone without removing the prosthesis).
What is radiation therapy for?
Radiation is a form of energy that is used to destroy tumors or microscopic tumor cells. It can be administered in several ways. The most common way is by an external beam. This is referred to as external beam radiation. It is used only in special circumstances when treating bone sarcomas. It is most commonly used when the tumor can not be removed surgically (when the tumor is unresectable) or when it can only be removed partially (an unresectable or partially resectable tumor rarely occurs however it most commonly occurs around the spine, pelvis and sacrum). In the case when the tumor can only be partially removed, radiation may be used to destroy the residual tumor cells. Rarely, radiation may be prescribed for some benign tumors, only under special circumstances. In general, I prefer to refrain from using radiation for benign tumors except for very extreme and unusual circumstances because of the risk that the radiation may turn the benign tumor into a malignant tumor (also known as malignant degeneration).
Whenever radiation is prescribed, the benefits of radiation must be weighed against the risks. The complications include stiffness and scarring, burns, muscle contractures, chronic swelling and lymphedema, muscle atrophy, muscle weakness, hair loss in the exposed area, skin burns, radiation induced cancers of bone and soft tissue, malignant degeneration of benign tumors, nerve damage, nerve pain, nerve paralysis. Radiation induced changes and damage continue to progress with time and compound year after year. The severity of these complications varies according to the dose of radiation administered and varies between patients. Most patients experience minor radiation induced changes or complications. Precautions are taken to minimize these complications. Physical therapy is required during and after radiation. Specific exercises should be continued for the rest of the patients life. The entire course of radiation depends upon the dose that is administered. Typically 3-4 weeks of treatment is required. The patient goes for the treatment daily, 5 days per week.
Radiation can also be delivered to the wound by catheters that are planted in the wound at the time of surgery. This is referred to as brachytherapy. I do not prefer to use brachytherapy because of the high wound complication rates that occur with its use. Additionally, in my opinion, it does not reliably deliver the radiation to all areas of the surgical bed where it is needed. I prefer external beam radiation delivered postoperatively. The required field is most reliably treated and since the radiation is administered when the wound is healed, wound complications are rarely an issue.
What surgical options are there?
Nowadays, most high grade bone sarcomas (malignancies; cancers) are treated with limb sparing surgery. (Limb sparing surgery refers to surgically removing the tumor without amputating the extremity). The bone that the tumor came from usually requires removal along with the joint that is next to the tumor. Once the tumor, bone and joint are removed, the defect (bone and joint) must be restored with a metallic endoprosthetic replacement or some alternative means of restoring the resected bone. Approximately, 95% of high grade bone sarcomas can be treated with limb sparing surgery. Amputations are rarely performed for primary tumors. If you have a bone sarcoma and you are told that you need an amputation, you should seek an additional opinion. The success of limb sparing surgery can be attributed largely to: the development of effective preoperative and postoperative chemotherapy protocols (kills the tumor and any residual cells which prevents the tumor from coming back after it is removed); advances and increasing experience with complex surgical techniques; the development of durable, mechanically sound and highly functional, metallic endoprosthetic bone and joint replacements; advances in imaging studies such as CT scans and MRIs which allow the surgeon to more accurately plan the surgery.
Almost all benign bone tumors (not cancerous) are treated less aggressively than the malignant bone tumors because they have less chance of coming back after being treated and they do not spread to other body parts. They are rarely ever treated with an amputation. Less complicated surgery is usually performed. Rarely must the bone and joint be resected (removed in entirety). Depending upon the type of tumor, the tumor can usually be curetted (scooped out of the bone). A high speed drill is used to shave the cavity walls until they appear normal. This is referred to as a resectional curettage. Liquid nitrogen (cryosurgery) may be used to freeze the tumor cavity and kill any residual microscopic tumor cells depending upon the type of tumor and its propensity to come back after curetting it; it is tehrefor eused primarily in the treatment of benign agressive tumors. Cryosurgery minimizes the risk of the tumor coming back. After curetting the tumor there is a bony defect (a hole in the bone) that can usually be fixed with methylmethacrylate (bone cement; the hole is filled with bone cement) and bone graft. Metallic rods, plates and screws may utilized to prevent the bone from fracturing (breaking).
Metastatic carcinoma to bone (metastatic cancer) is treated surgically if there is risk that the bone is going to fracture (break); if the bone has already fractured through the tumor; if there is a large soft tissue component ready to invade adjacent nerves, blood vessels, the chest or other critical structures; if the bone tumor represents the only site of metastatic disease (isolated site of metastatic disease). In instances where the tumor represents the only site of disease, the tumor may be treated surgically to remove all gross disease which may cure the patient or may make chemotherapy or immunotherapy protocols more effective. Radiation or other more conservative measures are often utilized if the patient does not meet these criteria or if the patient is too ill to undergo surgery. Surgery for metastatic carcinomas usually consists of stabilizing the bone with a rod and cement or with a long stem joint replacement. Occasionally the tumor will be removed with the bone and joint and the bone and joint will require a metallic endoprosthetic replacement with cement. In general, the operation that is chosen is the procedure that is most reliable with least chance of complications or faiure. It should be the procedure that will relieve the patient's pain and restore function most rapidly and reliably. Radiation may be prescribed postoperatively.
Several different surgical methods are used to treat bone tumors. The type of method that is chosen depends on the type of tumor; the grade of the tumor; the size of the tumor and the tumors inherent ability to come back after it is removed. The types of surgical procedures can be divided into several broad categories. A curettage refers to scooping the tumor out of the bone. This leaves a cavity in the bone (much like a cavity of a tooth). The sides of the cavity are scraped with hand curettes (instruments that look like small deep spoons with sharp edges) and typically shaved with a high speed drill (like a dental drill). The high speed drill removes additional microscopic tumor cells. A curettage is typically performed for benign tumors and metastatic tumors (carcinomas). Cryosurgery refers to freezing the tumor cavity to subzero temperatures with liquid nitrogen in order to kill residual microscopic tumor cells after the curettage and burr drilling. A curettage, alone, may be performed for benign tumors that have small to no risk of returning after the curettage. Curettage and Cryosurgery is performed for benign aggressive tumors (ie. Giant cell tumor); tumors that have a significant risk of coming back after a curettage alone. If these tumors come back they cause more bony destruction and become more difficult to cure. Once the tumor is removed, a hole in the bone exists that must be restored to prevent the bone from breaking and to allow function to return. The hole is usually filled with cement or a combination of cement and bone graft (bone from the patients own pelvic bone). Metal rods, screws and plates may be placed to give additional support to prevent a fracture after surgery. Stabilization procedures are usually performed for metastatic carcinomas. The tumor is usually curetted and packed with cement. Cryosurgery may be used and the bone is stabilized with a metal rod, screws or plates to fix or prevent any fractures from occurring, facilitate nursing care, restore function and relieve pain. Radiation may be prescribed postoperatively.
A limb sparing surgery is also called a resection. Resections are usually performed for malignant tumors and very large benign agressive tumors that have destroyed almost the entire bone. A radical resection is typically performed for high grade tumors. Limb sparing surgery can be performed for approximately 95% of malignant bone tumors. With a resection, the tumor is removed with the bone (or part of the bone) and usually the adjacent joint. The bone and joint must be restored. This part of the procedure is called a reconstruction. Usually a metal prosthesis (replica of the bone and joint) is used to restore (reconstruct) the bony and joint deficiency. Metal prostheses restore the patient to good function rapidly and are associated with few short term complications (ie. Infections) so that chemotherapy can be resumed promptly after surgery (few complications to delay chemotherapy if the type of tumor being treated requires chemotherapy). Ninety to 99% of prostheses last 10 years depending upon the anatomic site in which they are placed.An amputation refers to removal of the entire extremity without replacing it. There are several different types of amputations. The name given to the type of amputation depends upon how much of the limb is removed.
Some special names given to amputations are as follows:
Transmetatarsal amputation: removing the forefoot by cutting through the metatarsals
Chopart amputation: amputation through the midfoot closer to the ankle
Ankle disarticulation: amputation through the ankle joint (between the tibia/fibula and the talus)
Syme amputation: removal through the lower tibia
Below the Knee Amputation (BKA): amputation through the tibia and fibula (through the leg bones) usually approximately 6-8 inches below the knee
Above the knee amputation (AKA): amputation through the thigh bone
Hip disarticulation: Removal of the entire leg by cutting through the hip joint (between the femoral head and the acetabulum)
Hemipelvectomy: removal of the entire lower extremity including the same side of the pelvis
Extended hemipelvectomy: removal of the entire lower extremity including the same side of the pelvis and the sacrum on the same side.
Ray amputation: removal of a digit including a portion of the hand
Shoulder disarticulation: removal of the upper extremity (entire arm) by cutting through the shoulder joint (between the humeral head and the glenoid)
Forequarter amputation: removal of the entire upper extremity including the shoulder and scapula.
An orthopedic oncologist is an orthopedic surgeon who specializes in treating bone and soft tissue tumors. The orthopedic oncologist is specially trained in limb sparing surgery. Major amputations and stabilization procedures are also part of the specialty.