Bone Tumors and Tumor-Like Lesions

Bone tumors are diverse in their gross and morphologic features and range in their biologic potential from the innocuous to the rapidly fatal. This diversity makes it critical to accurately

diagnose and stage tumors, and treat them appropriately, so that the patients can not only survive, but also maintain optimal function of the affected body parts.

Most bone tumors are classified according to the normal cell or tissue of origin. Lesions that do not have normal tissue counterparts are grouped according to their distinct

clinicopathologic features ( Table 26-6 ). Overall, matrix-producing and fibrous tumors are the most common, and among the benign tumors, osteochondroma and fibrous cortical defect

are most frequent. Excluding malignant neoplasms of marrow origin (myeloma, lymphoma, and leukemia), osteosarcoma is the most common primary cancer of bone, followed by

chondrosarcoma and Ewing sarcoma.

The precise incidence of different bone tumors is not known because many benign lesions are not biopsied. Benign tumors outnumber their malignant counterparts, however, by at least

several hundredfold. Benign tumors have their greatest frequency within the first three decades of life, whereas in the elderly a bone tumor is likely to be malignant. In the United States,

about 2,100 new cases of bone sarcoma are

diagnosed annually, and approximately 1,300 deaths from bone sarcoma occur each year.

As a group these neoplasms affect all ages and arise in virtually every bone, but most develop during the first several decades of life and have a propensity to originate in the long bones

of the extremities. However, specific types of tumors target certain age groups and anatomic sites.[32] For instance, most osteosarcomas occur during adolescence, and about half of them

arise in the metaphysis around the knee, either in the distal femur or proximal tibia. These are the sites of greatest skeletal growth activity. In contrast, chondrosarcomas tend to develop

during mid- to late adulthood and frequently involve the trunk, limb girdles, and proximal long bones. Chondro-blastomas and giant cell tumors almost always arise in the epiphysis of

long bones; by comparison, Ewing sarcoma, osteofibrous dysplasia, and adamantinoma most often are centered in the diaphysis. Thus, the location of a tumor provides important

diagnostic information.

Although the cause of most bone tumors is unknown, genetic alterations similar to those that occur in other tumors clearly play a role. For instance, bone sarcomas occur in the Li-

Fraumeni and hereditary retinoblastoma cancer syndromes, which are linked to mutations in p53 and RB ( Chapter 7 ). Bone infarcts, chronic osteomyelitis, Paget disease, radiation, and

metal prostheses are also associated with an increased incidence of bone neoplasia. Such secondary neoplasms, however, account for only a small fraction of all skeletal tumors.

Clinically, bone tumors present in various ways. The more common benign lesions are frequently asymptomatic and are detected as incidental findings. Many tumors, however, produce

pain or are noticed as a slow-growing mass. Sometimes, the first hint of a tumor's presence is a sudden pathologic fracture. Radiographic analysis plays an important role in diagnosing

these lesions. In addition to providing the exact location and extent of the tumor, imaging studies can detect features that help limit diagnostic possibilities and give clues to the

aggressiveness of the tumor. Ultimately, in most instances, biopsy and histologic study are necessary. In addition to classifying the tumor, histologic grade must also be determined in

most primary malignancies. The histologic grade has been shown to be the most important prognostic feature of a bone sarcoma and is a key component of the major staging systems of

bone neoplasms.

Date: 2016-04-22; view: 941