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.
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.
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.
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.