Metastatic bone lesions on X-ray become visible when a primary cancer has spread to the bone. Many cancers can have spread to the bone. Most common cancers are breast, lung, and prostate. Often, a cancer diagnosis is known by the time cancer has spread to the bone.
Many bone metastasis are asymptomatic. Symptoms arise from bone pain. A mass arising from the bone can press on adjacent structures like nerves. Since metastasis weaken the bone, there can be a fracture. Complications such as fractures can be seen on X-ray.
Most metastasis occur more centrally sparing the extremities. Most commonly this would be to the spine, pelvis, ribs, skull, and upper arms and legs. Metastasis are most common to the marrow and than involve the cortex of the bone. It is less common to have spread to the peripheral extremities.
Bone metastasis on X-ray can have different appearances. Some can be sclerotic or whiter than the surrounding bone. Others can be like holes in the bone which we call lytic. Some cause an expansion of the bone. Others have mixed features. It takes a good amount of normal bone loss to see a metastasis on X-ray. Often we see the metastasis because there is destruction of the bone or the lesion is sclerotic or whiter than the surrounding bone.
There is little diagnostic uncertainty in most cases. A bone lesion in the setting of cancer becomes suspicious for spread. A bone scan nuclear study can evaluate the skeleton for the extent of metastasis. In cases of uncertainty, a biopsy of the bone can be done. A bone lesion in a cancer patient can be a dilemma, if it changes the treatment and prognosis.
Trestment of skeletal metastasis is often systemic. The target is the underlying cancer. Local therapies such as radiation or surgery are also done for lesions that are painful or in danger of causing a break. In addition to bone scan, PET scan is also very good at assessing the extent of cancer, throughout the body and in the bones.