Neoplasms of the musculoskeletal system are of various types, including osteogenic, chondrogenic, fibrogenic, muscle (rhabdo-myogenic), and marrow (reticulum) cell tumors as well as nerve, vascular, and fatty cell tumors. They may be primary tumors or metastatic tumors from primary cancers elsewhere in the body (eg, breast, lung, prostate, kidney). Metastatic bone tumors are more common than primary bone tumors.
BENIGN BONE TUMORS
Benign tumors of the bone and soft tissue are more common than malignant primary bone tumors. Benign bone tumors generally are slow growing and well circumscribed, present few symptoms, and are not a cause of death.
Benign primary neoplasms of the musculoskeletal system in-clude osteochondroma, enchondroma, bone cyst (eg, aneurysmal bone cyst), osteoid osteoma, rhabdomyoma, and fibroma. Some benign tumors, such as giant cell tumors, have the potential to become malignant.
Osteochondroma is the most common benign bone tumor. It usually occurs as a large projection of bone at the end of long bones (at the knee or shoulder). It develops during growth and then becomes a static bony mass. In fewer than 1% of patients, the cartilage cap of the osteochondroma may undergo malignant transformation after trauma, and a chondrosarcoma or osteosar-coma may develop.
Enchondroma is a common tumor of the hyaline cartilage that develops in the hand, femur, tibia, or humerus. Usually, the only symptom is a mild ache. Pathologic fractures may occur.
Bone cysts are expanding lesions within the bone. Aneurysmal (widening) bone cysts are seen in young adults, who present with a painful, palpable mass of the long bones, vertebrae, or flat bone. Unicameral (single cavity) bone cysts occur in children and cause mild discomfort and possible pathologic fractures of the upper humerus and femur, which may heal spontaneously.
A painful tumor that occurs in children and young adults is the osteoid osteoma. The neoplastic tissue is surrounded by reac-tive bone formation that assists in its identification by x-ray.
Giant cell tumors (osteoclastomas) are benign for long periods but may invade local tissue and cause destruction. They occur inyoung adults and are soft and hemorrhagic. Eventually, giant cell tumors may undergo malignant transformation and metastasize.