Bone metastases or osseous metastatic disease are cancerous lesions that the result of spread from another primary cancer (a cancer somewhere else in the body). They are more common than primary bone cancer. Some of the most common cancers to spread to bones are: breast, prostate, lung, kidney and thyroid.Metastatic disease affect the regular routine process of bone turnover. As a result, the structure of bone changes. There are two type of bone metastases, osteoblastic metastases and osteolytic metastases. Osteoblastic(sclerotic) metastases occur when cancer cells invade and cause too many bone cells to form. The bone then becomes very dense. Osteolytic metastases occur when the cancer breaks down too much bone resulting in the bone being destroyed and weakened. The former is the more common type.