The age of the patient is an important clue to assist the examiner in differentiating between lesions that may look the same but are unique to certain age groups. Conversely, the patient’s age may suggest a diagnostic possibility that would not otherwise be considered from the radiographic appearance because of an atypical presentation. Age is more helpful when the age range associated with the tumor is narrow. Given only the patient’s age, an examiner can determine which tumor is present with a high degree of accuracy. ⁶⁹ (Tables 13-1 and 13-2 present the ages at which common benign and malignant tumors develop, respectively.) Generally with malignant tumors, Ewing’s sarcoma and osteosarcoma are present in children, and metastatic bone disease and multiple myeloma are found in patients over 40 years of age. Benign tumors are most common in patients 10 to 30 years of age, slightly younger for simple bone cysts and slightly older for lipomas and hemangiomas.

Individual tumors often predispose to certain bones (Table 13-3). Even more suggestive is the longitudinal (diaphysis, metadiaphysis, metaphysis, and epiphysis) (Fig. 13-1) and transverse (central or eccentric medullary, cortical, periosteal, and parosteal) (Fig. 13-2) location within bone (Table 13-4 and Fig. 13-3).

A soft-tissue mass, created when the tumor mass breaks through the host bone’s cortex, suggests an aggressive tumor. Soft-tissue masses related to tumors distort but do not disrupt intramuscular soft-tissue planes; soft-tissue masses secondary to infections may. Tumors tend to respect soft-tissue boundaries; infections may not.

A number of pathologic processes are capable of accentuating or reviving normal mechanisms of bone growth resulting in periosteal or endosteal reactions. The appearance of the periosteal and endosteal reactions relates to the aggressiveness, intensity, and duration of the inciting process.

Periosteal and endosteal reactions must mineralize to be visible on radiographs; several patterns are identified (Fig. 13-4). Mineralization takes between 1 and 3 weeks. If the inciting process is indolent (e.g., vascular stasis), a thick, wavy periosteal reaction develops. Layered or lamellar periosteal reactions indicate a mildly aggressive underlying pathology (e.g., acute osteomyelitis). Aggressive pathology (e.g., osteosarcoma, Ewing’s tumor) may disrupt the periosteum, producing a radiating (sunburst) or parallel (hair-on-end) spiculated pattern (Fig. 13-5). The disrupted periosteum may form an acute angle with the cortex of the bone (Codman’s triangle) (see Fig. 13-4). Endosteal reactions are more limited, appearing thickened or scalloped in response to pathology within the medullary canal. Radiologic tumor grades based on the reaction of the host bone are presented in Table 13-5.

The tumor grade ultimately is derived from microscopic appearance of the tumor, as performed by a pathologist in association with the imaging findings and clinical data. Tumor staging (see Box 13-1) and grading relate inversely to the patient’s chance of survival.

A number of explanations exist as to why tumors produce bone destruction. Tumors may stimulate osteoclastic activity by direct pressure, local hyperemia, or invasion. Bone destruction may be permeative, moth-eaten, or geographic (Fig. 13-6). Geographic lesions generally are less aggressive than the more subtle moth-eaten– pattern lesions, which generally are less aggressive than the nearly imperceptible permeative pattern.

An observer’s ability to recognize bone destruction depends primarily on the size and location of the lesion. Destructive lesions in cortical bone are more easily recognized than those in cancellous bone because greater contrast exists between osteolytic lesions and compact bone than osteolytic lesions and cancellous bone. Although technical factors should be considered, in general, lesions in cancellous bone that are less than 1 cm in diameter are difficult to recognize. Moreover, 30% to 50% of cancellous bone may be destroyed before an osteolytic lesion is recognized on the most optimally exposed and processed radiographs. ^36,41,71,101 Osteolytic lesions in the diaphysis are more easily recognized because of the higher proportion of compact bone.

Each tumor has a unique growth rate influenced in part by the nature of the lesion and the response of the host bone. Markedly expansile lesions result when endosteal bone reabsorption of the inner cortex occurs in concert with periosteal appositional, intramembranous new bone growth of the outer cortex (Fig. 13-7). Although generally it is true that larger lesions are more aggressive than smaller ones, one should be careful not to judge a tumor’s clinical importance by size alone.

The rate of growth is a very important characteristic for assessing the aggressiveness of a lesion. Benign lesions grow slowly and have thick margins. Malignant lesions grow quickly and have less defined margins. Although highly important, the assessment of a lesion’s growth rate is difficult because of the usual lack of available serial studies.

The appearance of the zone of transition between a lesion and the host bone is probably the single best indicator of a lesion’s aggressiveness. An abrupt transition from normal to abnormal is a feature of benignancy. A wide transition is a feature of malignancy. The zone of transition is a direct reflection of the lesion’s aggressiveness and the response of the host bone to the lesion infiltration (Fig. 13-8). Margination describes the presence and thickness of the rim around the lesion. Malignant tumors typically are nonmarginated, a feature of their wide zone of transition (Figs. 13-8 and 13-9). Conversely, a lesion is most likely benign if surrounded by a sclerotic rim of varying thicknesses producing a narrow zone of transition. The presence of a thick margin is always accompanied by a short zone of transition and represents an attempt of the host bone to surround and limit a lesion’s growth. However, a short zone of transition is not always accompanied by a thick margin (e.g., giant cell tumor). The zone of transition should not be used as the sole criteria for determining the aggressiveness of the lesion. Even a well-marginated lesion can prove to be malignant in selected clinical circumstances. For example, a painful lesion presenting with a narrow zone of transition in a 60-year-old patient who has a previous history of a primary tumor should be considered bone metastasis until proved otherwise.

The matrix is the internal tissue, or substance, of a tumor. The radiographic appearance of the tumor’s matrix assists its categorization as primarily bone-, fibrous-, or cartilage-forming. Most bone tumors have a radiolucent matrix correlating to soft tissue. Only when the matrix is sufficiently mineralized with hydroxyapatite crystals will it become radiographically visible. Bone-producing tumors are radiodense. Highly aggressive bone-producing tumors appear less dense, with poorly formed osteoid material, than do nonaggressive bone-producing tumors. Tumors with a purely fibrous matrix appear radiolucent or slightly hazy (because of interspersed small bone fragments). Cartilage tumors usually are accompanied by irregular ringlike, flocculent, stippled, or flecklike radiodensities within the matrix (Figs. 13-10 and 13-11).

The presence of multiple lesions suggests different diagnostic possibilities than the presence of a single lesion. Generally radionuclide bone scanning determines if multiple lesions exist. Because radionuclide imaging is sensitive but not specific, plain film radiographs usually are taken at regions of increased radionuclide uptake. Radiographs usually are directed at evaluating a lesion rather than finding it. MRI and CT are applied less commonly to resolve uncertain findings of the radionuclide bone scan and plain films. The presence of multiple lesions limits the differential diagnosis. Common aggressive polyostotic diseases include metastatic bone disease and multiple myeloma. Less common possibilities include multicentric osteosarcoma and multifocal infections. Common nonaggressive polyostotic lesions include fibrous dysplasia, Paget’s disease, histocytosis, hereditary multiple exostoses (HME), multiple enchondromas (Ollier’s disease), and osteomyelitis.

A bone island (enostosis) is a commonly encountered entity, representing a region of compact bone located in cancellous bone (Fig. 13-12). ¹²⁸ Their etiology is not well documented, but most sources list them as developmental hamartomatous or dysplastic lesions. They may appear as a single defect or multiple defects with a variety of shapes. Bone islands are estimated to appear in 1% to 14% of the adult population without a demonstrated gender, age, or racial disposition.

Osteopoikilosis (spotted bone disease) is a relatively uncommon condition of skeletal dysplasia that is marked by a symmetric presentation of multiple bone islands. Each lesion is microscopically identical to a bone island.

Osteomas differ from enostoses in that the former protrude from the surface of the affected bone and are found in the skull. Also, bone islands are encountered in all age groups, whereas osteomas typically are discovered in the adult patient. Multiple osteomas may be one component of Gardner syndrome, comprising colonic polyposis, osteomatosis, dental lesions, and soft-tissue tumors. ^3,217

Enostoses are small (usually 0.1 to 2.0 cm), radiodense lesions that occur in all bones, although they are more common in the pelvis, proximal femora, and ribs. They have a characteristic thorny or spiculed border that blends into normal trabeculae, producing a typical whiskered or “brush border” periphery of the lesion (Fig. 13-13), a feature best seen on CT. Usually they are slightly oblong with their long axis running parallel to that of the host bone. Bone islands larger than 2 cm in diameter are less common, and are called giant bone islands. Larger lesions may exhibit active bone remodeling, evidenced by increased uptake of radiotracer with bone scintigraphy. ⁵³ Although most bone islands are stable in size, some do exhibit slow growth over time. ¹⁹ Bone islands appear as hypointense signals on MRI.

Osteopoikilosis exhibits a symmetric presentation common to the metaphyses of long bones, or commonly diffusely scattered in the carpals or tarsals. They may appear periarticular less commonly, especially about the hips (Fig. 13-14).

Osteomas appear as dense radiopacities found almost exclusively in the skull and facial bones, especially near the frontal sinuses (Figs. 13-15 and 13-16).

A bone island usually is identified readily because it occurs without symptoms and has a characteristic appearance on imaging. However, if bone islands are multiple, large, growing, or present in patients with clinical red flags of aggressive bone disease (e.g., pain at night, personal history of past malignancy), differentiation from an entity such as osteoblastic metastasis may be warranted. Past radiographs may help in this differential. If past radiographs are unavailable, a bone scan represents the traditional method of differentiating bone islands from more aggressive entities. ^96,183,215 However, it is possible that bone islands (especially large lesions) may appear active on bone scans, necessitating other methods of differentiation. MRI usually is definitive. Similar to a bone island, osteopoikilosis is not associated with clinical symptoms. Osteomas may become clinically significant if they enlarge and interfere with sinus drainage.

Osteoid osteoma appears as a small (<1.5 cm in diameter) osteolytic lesion with surrounding reactive sclerosis (Fig. 13-17). The central radiolucent nidus (FIG. 13-18FIG. 13-19 and FIG. 13-20) may be only a few millimeters in diameter and often contains a small focus of calcification. The surrounding reactive sclerosis may become so prominent that it completely obscures the radiolucent nidus, a feature that is particularly common when the lesions present in the vertebrae. The surrounding sclerosis represents a secondary finding and therefore may reverse after removal of the nidus. Osteoid osteomas are most commonly located in the cortex of long bones, usually the proximal femur (see Fig. 13-18) or tibia. Other locations include the posterior elements of the spine (e.g., concave side of painful scoliosis), humerus, hand, and talus. Osteoid osteomas usually are based in the cortex, but medullary, subperiosteal, and intracapsular locations do occur. ¹²²

Osteoblastoma appears as a larger (≥1.5 cm in diameter), geographic, expansile, generally nonaggressive, eccentric medullary lesion. It may exhibit a sclerotic component. Osteoblastomas are most commonly located in the posterior elements of the spine¹⁵⁷ (Fig. 13-21) and less frequently in the proximal femur, tibia, talus, ribs, and hands. ¹⁶¹

Because osteoid osteomas and osteoblastomas are richly vascularized, an intense uptake is noted on radionuclide bone scans. CT is valuable to further delineate the lesions and demonstrate a radiolucent nidus. This is particularly true when imaging areas of complex anatomy, such as the spine.

On MRI the central nidus shows low to intermediate signal intensity on both T1- and T2-weighted MRI scans, and enhancement after contrast administration. ²⁴⁶

Patients with osteoid osteomas and osteoblastomas often describe pain in the affected region. The pain begins as intermittent and vague, progressing to a dull and boring quality, which typically is not related to activity. Approximately 80% of patients with osteoid osteomas report a worsening of pain at night, which is characteristically alleviated by aspirin or other nonsteroidal antiinflammatory agents. ^106,209

Osteoid osteomas of the spine typically are located on the concave side of a painful scoliosis, and should be excluded in all children and young adults who present with unexplained back pain or painful scoliosis. ¹²⁴ Osteoblastomas also are associated with scoliosis but do not exhibit a predilection for the concave side. ¹³⁴Markedly expansile osteoblastomas may cause canal stenosis. An osteoid osteoma in a cortical location of the medial femoral neck may mimic clinically an impeding stress fracture or infection. En bloc surgical excision of the nidus and some surrounding sclerosis is the preferred treatment for both lesions. Often the excision of the radiolucent nidus of an osteoid osteoma is followed by dramatic relief of the patient’s complaint. ¹⁷⁰ Alternatively, long-term antiinflammatory treatment of 3 to nearly 4 years’ duration has been shown to regress the size of the lesion and provide permanent relief of symptoms. ¹²⁹ Cryotherapy has been applied successfully as adjuvant treatment.

Long bone ossifying fibromas typically occur within the first two decades of life and undergo a self-healing process until puberty and then stabilize. The mandibular lesions occur in the third and fourth decades and are much more common in females. ⁷⁷ There is no gender predilection for the long bone presentation. The long bone lesions occur de novo or in association with an adamantinoma.

Whether they are in the mandible or long bones, ossifying fibromas initially present as radiolucent lesions, stabilize, and then become sclerotic over time (Fig. 13-22). In the long bones, lesions present in the tibia, fibula, or both. In fact, synchronous lesions of the tibia and fibula that appear on one side of the body are common presentations. Individual lesions appear radiolucent, circumscribed, expansile, and eccentric. Lesions in the tibia have a propensity to locate in the anterior or anterolateral cortex, creating an anterior bowing deformity of the bone’s shaft. The mandibular lesions likewise may deform the lower margin of the mandible and may contain a target, central opacification.

Clinical concern for these rare lesions centers on differentiating them from typical fibrous dysplasia. Most lesions are treated conservatively.

Conventional osteosarcomas most commonly arise in the metaphysis of long bones, usually the distal femur (40%) (Fig. 13-23), proximal tibia (20%), humerus (9%), pelvis (5%), facial bones (5%), fibula (4%), and patella (<1%). Older patients exhibit a higher incidence of osteosarcoma in flat bones. The radiographic appearance of conventional osteosarcomas begins with a medullary osteolytic (25%), osteoblastic (25%), or mixed (50%) lesion in the metaphysis, often extending into the epiphysis or diaphysis. Ninety percent have a large, cloudlike density representing tumor bone and an aggressive (laminated, sunburst, “hair-on-end,” or Codman’s triangles) periosteal reaction (Fig. 13-24). The aggressive periosteal reaction occurs from tumor invasion lifting the periosteum of the bone, and subsequent reactive bone formation. A large soft-tissue mass is typical.

Telangiectatic osteosarcoma usually appears as an osteolytic, expansile lesion in the diaphysis of the femur, tibia, or humerus. It is characterized by periosteal reaction with a large soft-tissue mass and lack of visible bone production. The periosteal reaction often is layered, appearing as an “onion skin.” Parosteal osteosarcoma usually appears as a lobular, radiodense mass arising from a sessile base to surround the metaphysis of the host bone (FIG. 13-25FIG. 13-26FIG. 13-27FIG. 13-28 and FIG. 13-29). A thin radiolucent line is present but rarely seen, separating the tumor from the host bone. Nearly 70% of parosteal osteosarcomas are metaphyseal, arising from the posterior surface of the distal femur; other sites include the proximal tibia and humerus. Periosteal reaction is rare. Periosteal osteosarcomas present as soft-tissue masses extending from the diaphysis of long bones, usually the femur or tibia, which may have small perpendicular bone spicules or amorphous calcification within the tumor mass. The endosteal margin is not involved.

Secondary osteosarcomas appear as destructive lesions usually indistinguishable from conventional osteosarcomas, occurring in the region of primary disease. Extraosseous osteosarcomas appear as large soft-tissue masses, most often in the buttocks and thigh. ⁷⁹ More than half of the lesions demonstrate radiographic evidence of calcification. These lesions are best demonstrated by MRI. ²³⁴ Multicentric osteosarcoma is accompanied by multiple, symmetrically distributed radiodensities in the metaphyses.

For the most part, primary osseous lesions are well defined on conventional radiographs. CT and MRI are used to assess the extent of the lesion and evaluate its relationship to adjacent anatomy to aid surgical planning.

Conventional treatment includes the application of one or some combination of the following: excision, amputation, chemotherapy, and radiation. ^{52,164,194,227,244} Patient survival rates range from promising (with parosteal osteosarcoma) to poor (with multicentric osteosarcoma) and depend on the type of osteosarcoma, applied treatment, and general patient health status.

Numerous diffuse foci or larger nodular accumulations of malignant plasma cells are surrounded by areas of increased osteoclastic activity. MM represents the most common primary tumor of bone, although some consider MM a hematologic disease, making osteosarcoma the most common primary tumor of bone. In any case, MM is the most common malignancy to present as a primary skeletal site. A solitary lesion of plasma cell myeloma is termed plasmacytoma (Fig. 13-30).

It is believed that the abnormal plasma cells produce osteoclastic-activating factors²⁰³ and osteoblastic inhibitory factors, which leads to increased bone resorption and decreased bone formation. ^11,67 Initially MM invades the axial skeleton, progressing to the appendicular skeleton over time. It represents the most common primary malignant tumor of bone. Most patients with MM are 50 to 70 years old; rarely are those under the age of 30 years affected. ¹¹⁵ The median age is 60 years. A slight male predominance is often reported, and the lesions are twice as common among blacks as whites.

Approximately 80% of MM patients demonstrate radiographic features. Most commonly, MM occurs as multicentric (polyostotic) lesions of punched-out or moth-eaten patterns of bone destruction. Less commonly, MM presents as diffuse osteopenia without focal bone destruction; probably this is the most difficult presentation to recognize because it mimics osteoporosis. ³⁴

Up to 30% of MM patients initially exhibit only a solitary lesion of bone known as a plasmacytoma (FIG. 13-131FIG. 13-132 and FIG. 13-133). Plasmacytomas appear as large (typically >4 cm in diameter), expansile, and cystic lesions. About 70% of patients with solitary plasmacytomas progress to multifocal disseminated MM. ²⁴³

Rarely, MM presents as one or more sclerotic lesions, typically part of a larger syndrome known as POEMS (polyneuropathy, organomegaly, endocrinopathy, myeloma, and skin changes).

MM lesions exhibit a short zone of transition and no surrounding sclerosis, have no visible matrix (except for lesions in POEMS), and usually are less than 4 cm in diameter. MM originates in bones that are high in red marrow content. The skull, vertebral bodies, ribs, and proximal humerus and femur are most commonly involved (FIG. 13-34FIG. 13-35 and FIG. 13-36). Extraosseous manifestations are rare; they are found in fewer than 5% of patients. ^95,177 Ribs and other small bones may be slightly expanded when involved.

Neoplastic plasma cells produce an osteoclastic activating factor that stimulates massive osteolysis with only minimal bone reaction; therefore MM frequently is associated with a negative bone scan. Plain film radiography appears more sensitive than radionuclide bone scanning; however, both miss a significant portion of cases. MRI is highly sensitive and is used in cases of negative radiographs and radionuclide imaging. ²²⁹

Clinical findings are secondary to excessive plasma cell production. Pain is the most common patient complaint, reported in up to 70% of cases. Pathologic fractures are common and may be the presenting sign, especially collapsed vertebrae. MM is associated with multifocal bone pain (especially in the weight-bearing bones), amyloidosis, renal failure, hemorrhages, recurrent infections, and general weakness. ¹³⁶ Amyloidosis and related organ impairment is seen in association with about 10% to 15% of MM patients. ¹³⁰ Involvement of the kidneys and heart is most serious. In rare instances, patients with MM may remain asymptomatic. ^59,60

Laboratory examination may reveal hypercalcemia, hyperuricemia, elevated creatine levels, anemia, and thrombocytopenia. The plasma cells can accumulate in renal cells, causing dysfunction and renal failure. The amount of Bence Jones proteins in the urine is an indicator of the degree of renal involvement. Elevated serum renal chemistries such as BUN (blood urea nitrogen) and creatinine point to renal impairment from the deposition of immunoglobulins in the kidney.

The corresponding serum abnormality consists of hyperglobulinemia with a reversal of the albumin-globulin (A/G) ratio. Most patients produce an overabundance of the immunoglobulin G (IgG) type. Serum abnormalities are recognized by electrophoresis and are considered central to the diagnosis of the disease. The increased levels of monoclonal immunoglobulins (M component) can be detected by protein electrophoresis as an abnormal “M spike” or “M component spike.” The level of M component reflects the tumor’s burden and can be used as a surrogate index to monitor the course of the disease and its therapeutic outcome. For example, 0.5 g/dl of M component in the serum estimates 10 g of neoplastic tissue in the body. High levels of M component are seen with MM and Waldenström macroglobulinemia. Usually MM patients who exhibit only an isolated plasmacytoma do not exhibit the M component abnormality in their serum.

FIG. 13-31 A and B, Two cases of plasmacytoma presenting in the scapula (arrows). Both lesions exhibit the characteristic expansile, multiseptated lesions characteristic of the disease. B, This case is a arthrogram, exhibited by the injected contrast (crossed arrows).

FIG. 13-32 A and B, Plasmacytoma presenting as an expansile cystic defect of the ilium in two patients (arrows).

MM is diagnosed by a high index of clinical suspicion, with radiographic and laboratory correlation. A biopsy for histologic examination is necessary once a lesion is identified. Although variable, the usual course of the disease is that of gradual progression with a median survival of 3 years. ¹³⁷ Treatment includes radiation and chemotherapy.

FIG. 13-33 Plasmacytoma of the ilium appearing as a cystic, radiolucent lesion with mild expansion (arrows).

In 1921 James Ewing’s described a small, malignant round cell neoplasm of uncertain origin that bears his name. ⁷⁸ Traditionally Ewing’s sarcoma was thought to originate from noncommitted mesenchymal cells; however, more recent studies suggest an association between Ewing’s sarcoma and a neuroectodermal origin. ^55,150,248 Ewing’s sarcoma is the fourth most common primary malignant tumor of bone after multiple myeloma, osteosarcoma, and chondrosarcoma.

Ewing’s sarcoma of bone and soft tissue is one of four distinct histiologic subtypes of a group of lesions known as the Ewing’s family of tumors. The three other subtypes include peripheral neuroepithelioma (arising from the peripheral nervous system), esthesioneuroblastoma (developing from olfactive placode in the nasal vault), and Askin’s tumor (thoracopulmonary pediatric tumor).

Although Ewing’s sarcoma has been reported in patients from 5 months to 79 years old, 90% of cases involve patients younger than 30 years of age. ^72,182 It exhibits a strong predilection for whites^143,167 and a slight predilection for males.

Ewing’s sarcoma may occur in any bone of the body, although the majority of cases occur in the pelvis and long bones of the lower extremities (FIG. 13-37FIG. 13-38FIG. 13-39 and FIG. 13-40). A diaphyseal location is classic, but a metadiaphysis is more common. ^51,72

The radiographic appearance is marked by ill-defined, permeative, osteolytic bone destruction, cortical erosion (known as saucerization), laminated or “hair-on-end” periosteal reaction, and a large soft-tissue mass. ¹⁹⁹ Ewing’s sarcoma is less commonly a mixed osteolytic and sclerotic lesion (see Fig. 13-39). Only rarely does Ewing’s sarcoma appear as a predominantly sclerotic lesion. A Ewing’s tumor may appear similar to other round cell tumors, including lymphoma and metastatic neuroblastoma radiologically, but is differentiated from them easily with molecular probes and immunohistochemical techniques.

Ewing’s sarcoma is very aggressive; usually patients experience a history of diffuse pain and swelling involving the affected region. Other symptoms frequently include an elevated sedimentation rate, erythema, leukocytosis, and fever, mimicking osteomyelitis, a main differential diagnosis. It has a high likelihood of metastasis, especially common to the pulmonary tissue. The prognosis has been very poor traditionally, but recent combinations of irradiation, surgical resection, and multidrug chemotherapy have elevated the 5-year survival to nearly 70%. ³ Survival rates are influenced by the age of onset, location, gender, and size of the lesion.

Bone involvement with lymphoma occurs at any age and affects men more often than women. ¹⁹¹ The average age is 34 years; 50% of patients are between 10 and 30 years of age. ^25,45,83,213

Eighty-eight percent of patients with primary lymphoma of bone present with a single osseous lesion that fulfills the definition of primary NHL of bone (FIG. 13-41FIG. 13-42 and FIG. 13-43). ⁴⁵ The remaining cases are polyostotic at presentation. Four percent of all patients with systemic NHL present with a concurrent skeletal lesion. Twenty percent of patients with HD demonstrate concurrent osseous lesions. ^14,236

Osseous lesions caused by primary NHL of bone are radiographically indistinguishable from metastatic osseous lesions caused by systemic NHL and HD. ¹⁵³ All types of lymphoma usually exhibit a permeative or moth-eaten pattern of osteolytic bone destruction (Figs. 13-42 and 13-43). In the long bones, the diaphysis is preferentially involved. Soft-tissue masses are common, and periosteal reactions are infrequent. ²⁰² CT and MRI are useful to define the extent of the lesion, especially its soft-tissue component. Osteoblastic lesions are more common secondary to HD, often presenting as an “ivory vertebra” (Fig. 13-41).

Primary lymphoma of bone predominates in the lower extremities. Secondary (metastatic) bone involvement from systemic NHL and HD most commonly involves the spine, pelvis, and ribs. Burkitt’s lymphoma is most common in the mandible and maxilla (Fig. 13-44). ²⁹

Patients with osseous lymphoma typically complain of pain in the region of involvement but otherwise appear healthy. Radiation therapy, with or without adjuvant chemotherapy, may control the local bone lesions for years.

Plain film findings are abnormal in nearly 50% of children with leukemia. The most common radiologic manifestation of this cancer is generalized osteopenia. The earliest radiographic findings are transmetaphyseal lucent bands near the physes of long bones such as the femur and tibia (Fig. 13-45). Rather than leukemic infiltrates, these bands appear to represent a metabolic reaction to the process. Alternatively, they may develop because pressure on the physis from the neoplastic infiltrates alters bony maturation at the zone of provisional calcification.

Infiltration of the meninges of the brain creates a separation of the skull sutures in a small percentage of patients with leukemia. Based on the radiographic findings alone, differentiation of infiltration of the meninges from neuroblastoma metastasis to the skeleton can be challenging because both conditions cause periostitis and separations of the sutures.

Focal accumulations of leukemic cells have been identified in a small number of patients with acute myelogenous leukemia. Because of their green color, these cells have been termed chloromas, and are more common in adults. Most commonly chloromas accumulate outside the skeleton. Skeletal accumulations most often develop in the face, sternum, and ribs. ¹⁶

Patients with leukemia generally have a number of systemic complaints, including fever, malaise, and weakness. The musculoskeletal findings in leukemia include diffuse bone and joint pain, similar to the findings in juvenile rheumatoid arthritis. Joint and soft tissue swelling should alert the physician to the presence of a more serious condition. In leukemic patients the complete blood count (CBC) may be increased, normal, or decreased. However, the laboratory finding of blast cells in the peripheral blood smear is strongly suggestive of leukemia, and bone marrow biopsy is diagnostic.

A chondroma is a cartilage tumor involving enchondrally formed bones. If the chondroma is located within the medullary canal, it is called an enchondroma (Fig. 13-46). Less commonly it is found adjacent to the cortex beneath the periosteal membrane, known as a periosteal chondroma, juxtacortical chondroma, or perichondroma. Chondromas represent discrete islands of hyaline cartilage surrounded by lamellar enchondral bone. Enchondroma is the most common tumor occurring in the phalanges and is the second most common benign cartilage neoplasm of bone after osteochondroma. ⁹¹ Enchondromas most often present in patients 20 to 30 years old, with an equal gender distribution.

The presence of multiple enchondromas (enchondromatosis, or Ollier’s disease) increases the risk of malignant transformation by 30%. ^16,44,211 The combination of multiple enchondromas and subcutaneous hemangiomas is termed Maffucci’s syndrome and is associated with a 30% or greater increased risk for malignant transformation than occurs with solitary enchondromas. ^4,121,232 Malignant transformation is usually to a chondrosarcoma.

Juxtacortical chondromas are found in patients predominantly before the age of 30 years, ²³ appearing more commonly in males than females, at a ratio of 2:1.

Chondromas, whether medullary or juxtacortical, solitary or multiple, usually are found in the small bones of the hands, particularly the proximal phalanges (Figs. 13-47 and 13-48), and less commonly the feet (Fig. 13-49). The humerus, femur, and tibia also are involved.

An enchondroma appears as a well-defined medullary lesion, most often with some degree of calcification, endosteal scalloping (see Fig. 13-48), and bone expansion. Enchondromas are usually small, less than 3 cm in diameter (Fig. 13-50). On MRI the calcific foci appear as minute signal voids (Fig. 13-51). Enchondromas often are not as clearly outlined in long bones as when they appear in small tubular bones.

Malignant transformation to a chondrosarcoma is a rare event, occurring in less than 1% of patients. Malignant transformation occurs more often in proximal lesions (e.g., humerus versus phalanx), and is suggested by the disappearance of a previously noted pattern of matrix calcification.

Juxtacortical chondromas appear as soft-tissue masses with erosion or saucerization of the adjacent cortex (Figs. 13-52 and 13-53). Calcification is noted in 50% of juxtacortical chondromas. ²⁴⁰

Ollier’s disease appears with multiple (usually many) cystic defects of the hands, and less commonly the feet (FIG. 13-54FIG. 13-55FIG. 13-56 and FIG. 13-57). Soft-tissue hemangiomas are signified radiographically as soft-tissue masses with multiple phleboliths (Fig. 13-58).

Chondromas typically are asymptomatic. The presence of associated pain increases the clinical suspicion for the presence of pathologic fracture, malignant transformation, or a low-grade de novo chondrosarcoma. In addition, any chondroma that exhibits continued growth in a skeletally mature patient should be closely scrutinized to exclude malignancy because lesions typically stop growing in adult patients. Surgical curettage usually is indicated for substantial lesions.