Bone metastases, or metastatic bone disease, is a class of cancer metastases that results from primary tumor invasion to bone. Bone-originating cancers like osteosarcoma, chondrosarcoma, and Ewing’s sarcoma are rare. And, unlike hematological malignancies that originate in the blood and form non-solid tumors, bone metastases generally arise from epithelial tumors and form a solid mass inside the bone. Bone metastases cause severe pain, characterized by a dull, constant ache with periodic spikes of incident pain.
Sources of Bone Metastases
Bone is one of the most common locations for metastasis. While any type of cancer is capable of forming metastatic tumors within bone, the microenvironment of the marrow tends to favor particular types of cancer, including prostate, breast, and lung cancers. Particularly in prostate cancer, bone metastases tend to be the only site of metastasis.
Under normal conditions, bone undergoes a continuous remodeling through osteoclast-mediated bone resorption and osteoblast-mediated bone deposition. These processes are normally tightly regulated within bone to maintain bone structure and calcium homeostasis in the body. Disregulation of these processes by tumor cells leads to either osteoblastic or osteolytic phenotypes. Regardless of the phenotype, though, bone metastases show osteoclast proliferation and hypertrophy.