What is bone cancer?

Bone cancer is a sarcoma in the skeletal system. A sarcoma (originated from the Greek word “sarx” which means “flesh”) is a cancer that arises from transformed cells in one of the number of tissues that develop from the embryonic mesoderm. Two main types of cancers that are found in the bone are the primary bone cancer and the metastatic bone cancer.

Primary bone cancer, which is originated from the bone, is considerably less common than are metastatic lesions. The most common originating sites for bone metastatic are the prostate, breast, lung, kidney, gastrointestinal tract, and thyroid. The distinction between primary and metastatic bone tumours is straightforward in most cases but may be difficult in patients who present in solitary lesion without the history of a primary tumour in another site.

     Bone cancers are diverse in their gross and morphological features, and vary in their natural history from innocuous to rapidly fatal. It is very critical to diagnose these cancers correctly, stage them accurately, and treat them appropriately, so that the affected patients are able to survive from the sickness, and also maintain the optimal function of the affected body parts.

In 1999, there were about 2,600 cases of primary bone cancer and about 1,400 deaths related to this disease in the United States. A great deal of progress has been made to treat bone cancer. Only about 20% of people diagnosed with osteosarcoma survived for more than five years in the year of 1972. Today, as many as 80% of those diagnosed with localized bone cancer are able to live for more than 5 years.


Types of bone cancer

PRIMARY BONE CANCER

The most common type of primary bone cancer is osteosarcoma, which is also known as osteogenic sarcoma. This type of bone cancer originates in newly forming tissues, most often in the long bones of arms and legs. The second common type of bone cancer is chondrosarcoma, tumors made of abnormal cartilage. Ewing’s sarcoma is the third most frequent diagnosed bone cancer. This type of bone cancer believed to originate in immature nerve tissues. Ewing’s sarcoma is the most common bone cancer that affects children and teenagers. Other forms of bone cancer include chordoma, malignant giant cell tumor, adamantinoma, and reticulum cell sarcoma juxtacortical osteosarcoma.

Type of bone cancer

Common locations

Ages that will be affected (years)

Tissue of origin

Primary osteosarcoma

Metaphysis of distal femur, proximal tibia, and humerus.

10 - 20

Osteoid (bone)

Secondary osteosarcoma

Femur, humerus, and pelvis

> 40

Osteoid (bone)

Chondrosarcoma

Bones of shoulders, pelvis, proximal femur, and ribs.

40 – 60

Cartilage

Ewing’s sarcoma

Leg, hip, and arms.

10 – 20

Immature nerve tissues, usually in bone marrow

Chordoma

Upper/lower ends of spinal column or skull.

55 – 65

Cellular remnants of fetal spinal cords

Malignant giant cell tumor

Knee and vertebra.

40 – 55

Connective tissues of bone marrow

Fibrosarcoma of bone

Leg, hip, and arms

30 – 40

Connective tissues within bone marrow cavity


(a)    Osteosarcoma

Osteosarcoma is a malignant mesenchymal tumor in which the cancerous cells produce bone matrix. Exclusive of myeloma and lymphoma, osteosarcoma is the most common primary malignant tumor of bone that causes bone cancer. Osteosarcoma accounts for approximately 20% of primary bone cancers. Osteosarcoma occurs in all age groups. However, it has a bimodal age distribution: 75% occur in persons younger than 20 years old. The smaller second peak occurs in the elderly (over 60 years old). In 50% of this group, Paget’s disease (conditions known to predispose to osteosarcoma) is associated. Overall, men are more commonly affected than women with ratio 1.6 : 1.  


(b)   Chondrosarcoma

Chondrosarcomas are a group of tumors that span a broad spectrum of clinical and pathologic findings. Chondrosarcoma of the skeleton is about half as frequent as osteosarcoma and is the second most common malignant matrix-producing of bone. Unlike cartilage-forming osteosarcomas, the neoplastic cells in chondrosarcomas do not form osteoid. Futhermore, as compared with osteosarcomas, chondrosarcomas occur in older patients, usually in their 40s or older. Males are affected about twice as frequent as females. Chondrosarcomas commonly arise in the central portions of the skeleton, including the pelvis, shoulders, and ribs.


(c)    Ewing’s sarcoma

The Ewing sarcoma family of tumors encompasses the well-known Ewing sarcoma (EWS) of the bone, extraosseous EWS, primitive neuroectodermal tumor (PNET), neuroepithelioma, and Askin tumor. Among these, EWS and PNET are the most common, and they account for 6% to 10% of all primary bone tumors. Of all bone sarcomas, EWS/PNET has the youngest average age at presentation. Most affected individuals are between 10 to 15 years old, and approximately 80% are younger than 20 years old. Boys are affected slightly more frequently than girls.


(d)   Chordoma

Chordoma is a very rare type of tumor with an average survival of about six years after diagnosis. Chordoma occurs in adults over 30 years of age and is about twice as common in males as in females. It commonly affects either the lower or upper ends of the spinal column or skull.


(e)    Malignant giant cell tumor

Giant cell tumor is so named because it contains a mixture of mononuclear cells and a profusion of multinucleated osteoclast type giant cell. Giant cell tumor of bone is also known as osteoclastoma. Most cases arise in the epiphyses of long bones, particularly the distal femur, proximal tibia, proximal humerus and distal radius, and the vertebrae. It usually arises in individuals in their 40s, with slight female predominance. The histological of the giant cell tumor is incompletely understood. Current opinions suggest that the giant cell component is likely a reactive cell population derived from macrophages and only the accompanying mononuclear cells are neoplastic.


(f)    Fibrosarcoma

Fibrosarcoma is a much more rare bone cancer as compared to the others. It mostly affects individuals in their 30s to 40s, and is slightly more common in males than in females. Fibrosarcoma mainly affects the soft tissues of leg, behind the knees, hip, and arms. 


SECONDARY BONE CANCER

            Metastases are usually multiple, occasionally latent renal and thyroid cancers present as a single bony metastasis with pathological fracture. The incidence of bone secondaries especially in the spine is very high when these tumors become wide spread. Metastases are usually osteolytic with extensive destruction of bone. Osteoblastic activity is stimulated by the presence of tumor so that the dense reactive bone is formed in minority of the cases. Osteosclerotic secondaries of this type are seen particularly in cancers of the prostate and breast.


 

OTHER CANCER THAT DEVELOPS IN THE BONE

(a)    Non-Hodgkin lymphoma

Non-Hodgkin lymphoma usually develops in the lymph nodes but sometimes start in the bone. Primary non-Hodgkin lymphoma of the bone is often a widespread disease. This is because multiple sites of the body are involved. The outlook is about the same to other non-Hodgkin lymphomas of the same subtype and stage. Primary lymphoma of the bone is given the same treatment as lymphomas that are started in lymph nodes.

 

(b)   Multiple myeloma

Multiple myeloma is almost always found in the bones. However, doctors do not consider it as a primary bone cancer because multiple myeloma develops from the plasma cells of the bone marrows. Although it causes bone destruction, it is no more a bone cancer than is leukaemia. Multiple myeloma is treated as a widespread disease. Sometimes, myeloma can be first found as a single tumour, called plasmacytoma, in a single bone, but most of the times, it will go on to spread to the marrow of other bones.


Which part of the body does the cancer affect?

    Bone cancers are rare forms of cancers that can affect any bone in the body. There are 2 types of bone cancers namely bone sarcomas and multiple myeloma. Bone cancers can also happen when tumours start in other organs. This is known as secondary bone cancer. 




                

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