The presence of a neoplasm in bone is manifested in a variety of ways. Pain and localized swelling or pathologic fracture are the most frequent presenting complaints, but rarely is a bone tumor discovered as an incidental finding on radiographic images made for other reasons (e.g., after trauma). Occasionally, the appearance of new symptoms or a changing clinical picture in the presence of a known skeletal…

Myositis Ossificans Definition Myositis ossificans is a reactive, self-limiting condition characterized by prominent heterotopic ossification. It predominantly occurs deep in soft tissue, and it undergoes zonal maturation. If the lesion is located in the vicinity of bone (i.e., involves the structures of the bone surface), a periosteal reaction contributes to its formation. This may alter the classic clinicopathologic presentation of the lesion. For this reason, we…

Modern understanding of rachitic syndromes, originally referred to as vitamin D-resistant rickets, is based on the identification of a novel phosphate-regulating homeostatic system and its underlying diverse genetic background. Essential to this understanding were discoveries of two mutated genes involved in the development of somewhat overlapping yet distinct phosphaturic disorders. The first one involved the identification of phosphate regulating endopeptidase homolog on chromosome X ( PHEX…

Sclerosing bone lesions represent a unique group of dysplastic anomalies with a wide range of clinical presentations, radiographic characteristics, and genetic backgrounds. They can be separated into two major groups with hereditary and nonhereditary clinical presentations. A comprehensive description of all conditions included in the group is beyond the scope of this book. In this chapter, we describe some of these conditions that may occasionally simulate…

Synovial Chondromatosis Definition Synovial chondromatosis is a metaplastic condition involving articular or tendon sheath synovial membranes in which multiple nodules of cartilage are produced. Many of the nodules subsequently become detached from the synovial membrane and float in the joint. The process typically involves the synovium diffusely, has a high propensity for recurrences, and may severely compromise the function of a joint. The exact pathogenesis of…

In evolutionary biology, the notochord or chorda dorsalis is typically discussed as a prototypic internal skeleton of prevertebrate animals. In vertebrates, the notochord exists transiently and in addition to providing structural integrity to the embryo, it secretes factors that are essential for body patterning with respect to the dorsal-ventral and left-right axes. These signals are required for positional orientation and fate information concerning the development of…

An epithelial neoplasm originating in the long bones of the skeleton, referred to as adamantinoma, which almost exclusively affects the tibia and fibula, and its relationship to a coexisting peculiar fibroosseus lesion, has been intriguing both pathologists and clinicians for more than a century. In 1913, Fischer described a peculiar tumor occurring predominantly in the tibia and occasionally in the fibula that was somewhat similar to…

Lipoma Definition Lipoma is a rare primary tumor of bone composed of mature adipose tissue. Lipomas involving bone are divided into three types: intramedullary (intraosseous), intracortical/subperiosteal, and parosteal. Lipomas involving synovial tissue are described in Chapter 20 . Incidence and Location Lipomas of bone are extremely rare; fewer than 50 cases are described in the literature. Intramedullary Lipoma Intramedullary lipomas usually occur in the metaphyseal parts…

Cystic lesions of bone represent a heterogeneous group of entities in which the common feature is de novo formation of unilocular or multilocular cavities filled with blood, serous fluid, mucinous content, or keratin debris. Secondary cystic changes in preexisting conditions, such as in chondroblastoma, fibrous dysplasia, and giant-cell tumor, are discussed in conjunction with those underlying conditions. The development of secondary aneurysmal bone cyst engrafted on…

The complex architecture of the human body requires an efficient life-support system that transports gases, liquids, and other nutrients as well as circulating cells that play important roles in body defense systems. These interacting tasks are carried out by a system that is ubiquitous to all vertebrates and comprises two treelike branched systems of tubules known as blood and lymphatic vessels lined by highly specialized endothelial…

In the early 1920s, James Ewing identified a peculiar round-cell tumor that he called diffuse endothelioma of bone. The tumor predominantly affected the long tubular bones of young patients. This lesion was distinguished from the general category of unclassified round-cell sarcomas and lymphohematopoietic tumors based on its clinicopathologic features (i.e., small, round-cell morphology), a predilection for the long tubular bones of skeletally immature patients, and the…

Giant cell lesions form a group of entities with diverse clinical presentations and behaviors unified by the presence of a prominent population of multinucleated giant cells. They have been, by convention, divided into two major groups: those that were considered to be truly neoplastic and those that were perceived as being reactive in nature. The prototypic example of neoplastic giant cell lesions is a giant cell…

Nonossifying Fibroma (Fibrous Cortical Defect) Definition The terms nonossifying fibroma (nonosteogenic fibroma), fibrous cortical defect, and metaphyseal fibrous defect have been applied to the same metaphyseal fibrohistiocytic process. The location of the lesion in the growing portions of long tubular bones of skeletally immature patients and its frequent spontaneous resolution indicate that it represents a self-limiting process most likely related to incomplete ossification. Incidence and Location…

Fibrous Dysplasia This disorder was recognized as a clinical syndrome of disseminated skeletal deformities long before it was given the name fibrous dysplasia by Lichtenstein and Jaffe in two classic publications that appeared in 1938 and 1942. In older literature, it had been discussed under the term osteitis fibrosa or generalized fibrocystic disease of bone, which also included such conditions as renal osteodystrophy and hyperparathyroidism. The…

Chondrosarcoma is the second most frequent primary malignant tumor of bone. It represents one fourth of all primary bone sarcomas. The term chondrosarcoma is used to describe a heterogeneous group of lesions with diverse morphologic features and clinical behavior. The behavior of these lesions ranges from slowly growing, nonmetastasizing tumors to very aggressive metastasizing sarcomas. More than 90% of these tumors are designated as conventional chondrosarcomas.…