bone metastasis
Meaning of bone metastasis: Cancer that has settled in bone, where it keeps the name of the organ it started in rather than the bone it now occupies.
Definition of bone metastasis
A bone metastasis is a deposit of cancer that has traveled from a tumor elsewhere in the body and taken hold in bone. The cells keep the identity of the original organ, so breast cancer found in the spine is still breast cancer and is treated as such. The spine, pelvis, ribs and the upper ends of the thigh and arm bones are involved most often.
Which cancers spread to bone?
Cancers of the breast, prostate, lung, kidney and thyroid account for the majority. The favored sites share a feature: they are the bones that still contain active red marrow in adult life, with a rich and slow blood supply that lets circulating cells settle. Once there, the tumor cells manipulate the normal cycle of bone removal and rebuilding, which is what produces the damage. Distinguishing this from bone cancer arising in the bone itself matters, because the two are entirely different diseases with different treatments.
What does a deposit do to the bone?
| Pattern | What happens | Typical origin |
|---|---|---|
| Lytic | Bone is dissolved away, leaving holes and weakness | Kidney, lung, thyroid, myeloma |
| Blastic | Dense disordered new bone is laid down, strong on a scan but structurally poor | Prostate |
| Mixed | Both processes together | Breast |
What problems follow?
Pain is the commonest, often worse at night and at rest rather than with movement. Weakened bone can break under ordinary load, a fracture that may be the first sign of the disease. A deposit in a vertebra can collapse and press on the spinal cord, producing back pain with leg weakness, numbness or loss of bladder control, a situation treated as an emergency because delay costs function permanently. Bone breakdown releases calcium, and a high level causes thirst, constipation, drowsiness and confusion. Extensive marrow involvement lowers blood counts.
How is it found?
A bone scan surveys the whole skeleton for areas of raised turnover. CT shows the structure and the fracture risk, and MRI is best for the marrow and for the spinal cord. Plain x-rays are insensitive early, since a large share of the mineral at a site must be lost before anything appears. Where the origin is unknown, a biopsy identifies the tissue of origin. The same reasoning applies to brain metastasis and other secondary sites.
Also known as
Used in a sentence
Imaging confirmed widespread bone metastasis involving the thoracic spine and pelvis.
Good to know
A cancer in bone that began elsewhere is not bone cancer, and the distinction determines treatment, since the deposit responds to therapy directed at the original tumor type.
Word origin
Where “bone metastasis” comes from
Metastasis is Greek, from meta, meaning change or beyond, and stasis, meaning a standing, so a shift of position.