Primary tumors of bone are relatively uncommon in comparison with secondary or metastatic neoplasms. They are, however, of great clinical significance because some grow rapidly and metastasize widely. Although tumors of bone have been categorized classically as
primary or secondary, there is some disagreement about which tumors are primary to the skeleton.
Tumors of mesenchymal origin that reflect skeletal tissues (eg, bone, cartilage, and connective tissue) and tumors developing in bones that are of hematopoietic, nerve, vascular, fat cell, and notochordal origin should be differentiated from secondary malignant tumors that involve bone by direct extension or hematogenous spread. Because of the great variety of bone tumors, it is difficult to establish a satisfactory simple classification of bone neoplasms.
Persistent skeletal pain and swelling, with or without limitation of motion of adjacent joints or spontaneous fracture, are indications for prompt clinical, radiographic, laboratory, and possibly biopsy examination. Radiographs may reveal the location and extent of the lesion and certain characteristics that may suggest the specific diagnosis. The so-called classic radiographic findings of certain tumors (eg, punched-out areas of the skull in multiple myeloma, “sun ray” appearance of osteogenic sarcoma, and “onion peel” effect of Ewing’s sarcoma), although suggestive, are not pathognomonic. Even a bone tumor’s histologic characteristics, considered in isolation, provide incomplete information about the nature of the disease. The age of the patient, the duration of complaints, the site of involvement and the number of bones involved, and the presence or absence of associated systemic disease—as well as the histologic characteristics—must all be considered for proper management.
The possibility of benign developmental skeletal abnormalities, metastatic neoplastic disease, infections (eg, osteomyelitis), posttraumatic bone lesions, or metabolic disease of bone must always be kept in mind. If bone tumors occur in or near the joints, they may be confused with the various types of arthritis, especially monarticular arthritis.
Specific Bone Tumors
Tumors arising from osteoblastic connective tissue include osteoid osteoma and osteosarcoma. Osteoid osteomas are benign tumors of children and adolescents that should be surgically removed. Osteosarcoma, the most common malignancy of bone, typically occurs in an adolescent who presents with pain or swelling in a bone or joint (especially in or around the knee). Since the symptoms often appear to begin following a sports-related injury, accurate diagnosis may be delayed. Osteosarcoma can also develop in patients with Paget’s disease of bone, enchondromatosis, fibrous dysplasia, or hereditary multiple exostoses. Osteosarcomas are treated by resection and chemotherapy, with 5-year survival rates improving from 15% in 1965 to 60% at this time. Fibrosarcomas, which are derived from nonosteoblastic connective tissue, have a prognosis similar to that of the osteogenic sarcomas. Tumors derived from cartilage include enchondromas, chondromyxoid fibromas, and chondrosarcomas. Histologic examination is confirmatory in this group, and the prognosis with appropriate curettement or surgery is generally good.
Other bone tumors include giant cell tumors (osteoclastomas), chondroblastomas, and Ewing’s sarcoma. Of these, chondroblastomas are almost always benign. About 50% of giant cell tumors are benign, while the rest may be frankly malignant or recur after excision. Ewing’s sarcoma, which affects children, adolescents, and young adults, has a 50% mortality rate in spite of chemotherapy, irradiation, and surgery.
Although prompt action is essential for optimal treatment of certain bone tumors, accurate diagnosis is required because of the great potential for harm that may result from temporization, radical or ablative operations, or unnecessary irradiation.
Neurogenic arthropathy is joint destruction resulting from loss or diminution of proprioception, pain, and temperature perception. Although traditionally associated with tabes dorsalis, it is more frequently seen in diabetic neuropathy, syringomyelia, spinal cord injury, pernicious anemia, leprosy, and peripheral nerve injury. Prolonged administration of hydrocortisone by the intra-articular route may also cause Charcot’s joint. As normal muscle tone and protective reflexes are lost, secondary degenerative joint disease ensues, resulting in an enlarged, boggy, painless joint with extensive cartilage erosion, osteophyte formation, and multiple loose joint bodies. Radiographic changes may be degenerative or hypertrophic in the same patient.
Treatment is directed against the primary disease; mechanical devices are used to assist in weight bearing and prevention of further trauma. In some instances, amputation becomes unavoidable.