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Notochordal and Related Lesions

The notochord is a rod-shaped structure that forms during the third week of gestation and organizes formation of the axial skeleton. As vertebral bodies undergo ossification, the notochord becomes fragmented, and by the second month of development, notochordal tissue is typically only present in the intervertebral space, forming the nucleus pulposus of the intervertebral disk. Because of this process of notochordal degeneration, notochordal tissue is not…

Metastases to Bone

Overview Metastases to bone of tumors from nonosseous primary sites account for the largest percentage of bone tumors. The host bone responds either by osseous resorption (osteolytic), osseous formation (osteoblastic), or often both processes. This chapter will cover the clinical and radiologic features as well as the pathologic classification of metastases to bone in adults and children. Pathophysiology (Microenvironment) Metastases to bone occur either by direct…

“Soft Tissue” Tumors of Bone, Avascular Necrosis and Bone Infarct, and Paget Disease

Benign “Soft Tissue” Tumors Primary in Bone Schwannoma Definition and Synonyms Schwannoma, also known as neurilemmoma and neurinoma, is a benign nerve sheath tumor that occurs primarily in soft tissue but can also occur primarily within bone or secondarily involve bone. Incidence and Demographics Intraosseous schwannomas are rare, with a reported incidence of less than 1%. They typically affect young adults in the second to fifth…

Cystic Lesions in Bone

Cystic lesions of bone comprise a diverse number of entities, including simple or unicameral bone cyst, aneurysmal bone cyst (ABC), epidermal cyst, and intraosseous ganglion. Simple bone cysts are typically lesions of boys in the long bones and are relatively easy to recognize on conventional imaging and histopathology. They are treated with a combination of curettage, bone grafting, and injection of steroids into the luminal cavity.…

Lesions Characterized by Permeation of Cells through Trabecular Bone with or without Bone Destruction

Permeative lesions involving the bone represent many different disease processes and radiographically may mimic one another. The permeative lesions discussed in this chapter represent a diverse group that include benign tumors, malignant tumors, a variety of histiocytic disorders, hematolymphoid-derived tumors that primarily involve bone, and osteolytic lesions secondary to localized or systemic infection. These entities have certain histomorphologic, immunocytochemical, and molecular features that provide for a…

Vascular Tumors of Bone

Vascular tumors of bone are defined as a neoplastic proliferation of endothelial cells that are biologically benign or malignant. This is a heterogeneous group of tumors; it includes a wide variety of different clinicopathologic entities whose biological potential ranges from those that are relatively indolent and slow growing to those that are extremely aggressive and frequently fatal. Clinically significant vascular tumors are infrequent and account for…

Lesions Characterized by a Fibrous Spindle Cell Proliferation Replacing Trabecular Bone

Fibro-osseous Lesions Fibrous Dysplasia Overview Fibrous dysplasia of bone was historically thought to be a developmental anomaly of fibrous tissue and bone but is now known to be secondary to defined mutations in the GNAS gene. Histologically, the osseous component is composed of irregularly distributed woven bone, and osteoblasts are usually not easily recognized in these lesions by conventional brightfield microscopy. The background fibrous component is…

Lesions Characterized by Large Numbers of Giant Cells Replacing Trabecular Bone

Many bone tumors contain large numbers of osteoclast-like giant cells. However, two lesions have many overlapping histologic findings and may pose a particularly difficult problem in differential diagnosis. These lesions are conventional giant cell tumor of bone and giant cell reparative granuloma. As in all bone pathology, the distinction cannot be made solely on histologic grounds. Careful considerations of conventional radiographic features as well as the…

Lesions Characterized by Cartilage Deposition and Aggressive Radiology

The vast majority (greater than 85%) of skeletal chondrosarcomas are conventional chondrosarcomas, which is a family constituted of primary central chondrosarcoma, primary peripheral chondrosarcoma, secondary central chondrosarcoma, secondary peripheral chondrosarcoma, and periosteal chondrosarcoma. The other entities to be considered in this chapter include clear cell chondrosarcoma, dedifferentiated chondrosarcoma, and mesenchymal chondrosarcoma. Chondrosarcomas are among the most common primary sarcomas of bone (20% to 30%) yet are…

Lesions Characterized by Cartilage Deposition and Nonaggressive/Intermediate Radiology

Chondroblastoma Definition and Synonyms Chondroblastoma is a benign cartilage-forming neoplasm occurring in the epiphyses of immature long bones. Brief Historical Overview Chondroblastoma was originally called a “calcifying giant cell tumor” by Ewing and “epiphyseal chondromatous giant-cell tumor” by Codman. In 1942, Jaffe and Lichtenstein recognized this entity as distinct from the so-called giant cell tumor variants under the name “benign chondroblastoma.” Incidence and Demographics Chondroblastoma is…

Juxtacortical Lesions

Juxtacortical lesions of bone are a group of entities with differing histogenesis and pathogenesis that arise in association with the periosteum. Periosteal stromal cells participate in fracture repair, and as such, they are able to differentiate into fibroblastic, osteoblastic, and chondroblastic lineages. Therefore, lesions of the periosteum present a variety of tissue components, particularly in those entities considered to be reactive, proliferative lesions. In many cases,…

Lesions Characterized by Osteoid Deposition and Nonaggressive Radiology Located on Bone Surface

Osteochondromas and Hereditary Multiple Osteochondroma Definition and Synonyms Osteochondroma, also known as exostosis or osteocartilaginous exostosis, is characterized by a cartilage-capped bony outgrowth containing a marrow cavity with continuity to the underlying bone. Historical Background Osteochondromas are the most common benign bone tumors. The tumors occur exclusively in bones of endochondral origin and thus predominantly arise from the metaphysis of long bones, especially those around the…

Lesions Characterized by Osteoid Deposition and Aggressive Radiology Located within Bone

Osteosarcoma (also known as osteogenic sarcoma) includes lesions ranging from low grade and indolent to high grade and aggressive, but in all cases osteoid matrix is directly produced by neoplastic cells. Histologically diverse, it includes tumors that mimic giant cell tumor, Ewing sarcoma, aneurysmal bone cyst, osteoblastoma, chondrosarcoma, and fibrous dysplasia. It is the most common primary bone sarcoma. Conventional Osteosarcoma Conventional osteosarcoma is a high-grade…

Lesions Characterized by Osteoid Deposition and Nonaggressive Radiology

Osteoma/Bone Island Definition and Synonyms Osteoma and bone island or enostosis are benign slow-growing non-neoplastic lesions composed of dense mature compact or cancellous bone. The basic difference between the two is their location—osteoma being a surface (parosteal, periosteal) lesion, whereas bone island an intramedullary lesion. Brief Historical Overview A literature search yielded two case reports of surgical management for orbital osteoma by Norris and Fridenberg, dated…

Patterns of Diagnostic Evaluation

The diagnostic pathology of bones and joints is not significantly more complicated than the pathology of other body sites, but tissues that are essentially invisible to an examining physician and that then must be sawed and decalcified can be technically and diagnostically challenging. In addition, the imperative for radiographic correlation with bone specimens may intimidate pathologists who are not familiar with clinical imaging studies. Until the…

Clinical Patterns of Orthopedic Disease

It is often said—only partly in jest—that orthopedic surgeons need to distinguish only two disease processes: fracture and degenerative arthritis. Although it is true that much of clinical orthopedic practice focuses more on the technical details of exactly what anatomy is directly involved in a given fracture or degenerative joint, as well as how best surgically to manage it, there is a broad complexity of other…

Patterns in Radiology

Solitary bone lesions and soft tissue masses are commonly encountered in general orthopedic practice. Emphasis in this chapter will be on the radiographic appearance of solitary bone lesions. However, advanced imaging patterns will also be discussed, especially in the setting in which radiographic imaging contributes little to the evaluation of such lesions. With lytic and blastic bone lesions, radiographs often provide a discrete differential diagnosis. In…

Normal Bone Anatomy

Definitions and Synonyms Cortex: the dense outer portion of a bone; also referred to as compacta Medulla: the inner part of a bone contained inside the cortex. It may be composed of marrow and fat in the midportions of long bones, or marrow, fat, and coarse cancellous bone near the bone ends. Cancellous bone is sometimes called spongiosa. Primary spongiosa: cancellous bone consisting of mixed spicules…

Cirrhosis: A Term in Need of a Makeover

Acknowledgments Dr. Sempoux extends very special thanks to Professor Darius Moradpour and Dr. Sabine Schmidt-Kobbe (CHUV, Lausanne, Switzerland) for their critical clinical advice in formulating this chapter. The term cirrhosis is derived from the Greek word “kirrhos” meaning “yellow” or “tawny” in reference to the color of the nodules observed at the liver surface. The first known description of this condition dates back to Hippocrates in…

Regression of Liver Fibrosis: From Myth to Reality

Abbreviations CPA collagen proportionate area ECM extracellular matrix HRC hepatic repair complex HSC hepatic stellate cell MF myofibroblast MMP matrix metalloproteinase SMA smooth muscle actin TIMP tissue inhibitor of metalloproteinase Regression of fibrosis is no longer a mythical concept. First challenged by Perez Tamayo in 1979, the dogma of irreversibility of liver fibrosis (and cirrhosis) has been firmly submerged by abundant experimental and clinical evidence to…