Bone cancer develops when cells within bone tissue develop genetic mutations that allow the cells to proliferate out of control. Osteoblastic bone cancers lead to the development of abnormal bony growths on the bone tissue, while osteolytic bone cancers eat away at healthy bone tissue as the cancer grows. In the early stages of bone cancer, before advanced tumor development, the cancer is generally localized within one bone, or a region of one bone. If the cancer is left untreated, it can progress to the more harmful, late stages of cancer.
Stage II: Development of a High Grade Tumor
In end-stage bone cancer, the bone cells will take on a high-grade appearance. Earlier-stage, low-grade bone tumors contain cells that, although they proliferate abnormally, still resemble bone cells. In late-stage bone cancer, the cancer cells take on an embryonic and stem cell-like appearance, and these stem cell-like cells are the hallmark of high grade tumors.
Bone cancers that are localized on the bone that contain high-grade tumor cells are considered stage II cancers. Stage II bone cancers are further characterized depending on their size: Stage IIA cancers are smaller than three inches in diameter, while stage IIB cancers are larger than three inches, reports the American Cancer Society.
Stage III: Invasion of Neighboring Tissue
If stage II bone cancer is left untreated, the cancer cells will begin to colonize neighboring tissue. Normal bone tissue cells have an extremely limited ability to migrate, since they develop into fully mature cells surrounded by hard bone tissue called the matrix. High-grade cancer cells, such as those seen in stage III bone cancers, are more stem cell-like and are able to migrate to other tissues. Stage III cancers are characterized by cancerous growths on more than one region of the affected bone, reports the American Cancer Society. If left untreated, stage III cancers will become more migratory and advance to stage IV, metastatic bone cancer.
Stage IV: Metastasis
Stage IV bone cancer develops when a bone cancer gains the ability to metastasize--travel throughout the body to colonize in distant organs. Bone cancer can metastasize to other bones or to other tissues such as the brain, lungs or liver, reports MayoClinic.com. Bone cancer metastasis can be devastating and fatal, since cancer metastases can lead to difficulty breathing, seizure, or diminished liver function leading to organ failure. Treatment for metastatic bone cancer may include chemotherapy or targeted therapies in an effort to kill cancer cells throughout the body. In many cases, treatment for metastatic bone cancer is palliative, and may include surgery to remove cancer metastases that are causing pain to increase the patient's quality of life.
