Bone tumors can be of two different types. They may arise from the bone tissue, and we call them primary bone tumors. But we also have secondary bone, those that metastasize from other tumors and form secondary metastatic masses in the bones.
Primary bone tumors are relatively rare after the fourth decade of life and less frequent as compared to secondary bone tumors. Primary bone tumors can be either benign or malignant. Bone tumors can be classified according to the type of cells in the tumors as bone-forming tumors, cartilage-forming tumors, giant cell tumors, and bone marrow tumors.
Benign bone-forming tumors include osteoma, osteoid osteoma, and osteoblastoma. The malignant counterparts include primary and secondary osteosarcoma. Cartilage-forming benign tumors of the bone include osteochondroma, enchondroma, chondroblastoma, and chondromyxoid fibroma. The malignant cartilage-forming bone tumors are named chondrosarcoma. Giant cell tumor of the bones is also known as osteoclastoma, which is usually benign, but if left untreated, it can transform into a malignant tumor. The last type is bone tumors that arise from bone marrow, and they include Ewing’s sarcoma, lymphoma, multiple myeloma, and plasma cell tumors.
Metastatic tumors of the bones are usually osteolytic, which means that they dissolve the bone and cause multiple fractures. In contrast, some other metastatic tumors, such as those from the prostate, are commonly osteoblastic, meaning that they form new bone and increase the brittleness of the bones.
The development of bone tumors is not associated with any previous pathology. Still, some conditions are associated with the development of bone tumors such as RB gene mutation (retinoblastoma) in the case of osteosarcoma. Other conditions rarely associated with bone tumors are chronic osteomyelitis, Paget’s disease, infarction, metal orthopedic prosthetics, and radiation exposure. Melanoma is the most common malignant tumor of the bone, followed by osteosarcoma and chondrosarcoma, which are the second and third most common, respectively.
Patient with bone tumors may have the following clinical features:
Location of the tumor
There is not a single location of the bone tumor. It depends on the type of tumor. Osteoid osteoma is seen in the tibia, humerus, and femur, especially the femoral neck, while osteoma affects mostly the skull, facial bones, and sinuses. Osteoblastoma affects the vertebral column and the long bones, including the femur, humerus, and tibia. Chondromas affects tubular bones of the hands and feet in 50% of cases, and it is also seen in the femur, humerus, and ribs.
Giant cell tumors are seen in the distal femur and proximal tibia (above and below the knee), it is also seen in the distal radius, near the wrist, or the proximal humerus (away from the elbow). Osteosarcoma occurs in the distal femur (45%), tibia (15%), and proximal humerus (10%). Chondrosarcoma is seen in the pelvic bones, femur, rib, and pectoral girdle (shoulder). Ewing’s sarcoma is mostly seen in the midshaft of the femur, but also the tibia, and humerus. The bones that are mostly affected by secondary metastatic masses are vertebral bodies, ribs, the upper end of the femur and the humerus, and the pelvic bones because they have a rich blood supply and contain bone marrow.