Multiple Radiolucent Defects Lytic Lesions

► [Cyst-like bone defects, focal bone destruction]

Multiple radiolucent bone defects occur in a relatively small group of skeletal dysplasias and syndromes, and they often display features that are characteristic of a specific disorder. In contrast, lytic lesions are associated with a number of disorders, including neoplasms, infections, and metabolic disorders, whose diagnosis is rarely reached without biopsy. The radiolucent bone defects are cyst-like, expansile lesions in which the normal bone tissue has been replaced either by slow-growing dysplastic tissue or by an accumulation of pathologic material. These lesions usually have well-defined margins, and they are primarily intramedullary, with secondary scalloping of the cortex. Unlike true cysts of bone, which are by definition single lesions and uni- or multiloc-ulated, radiolucent defects are multiple cavities that lack internal epithelial covering and do not contain fluid. On the other hand, lytic lesions are usually ill-defined areas of bone radiolucency and display a moth-eaten or permeative pattern of bone destruction. However, the radiographic differentiation between cyst-like and lytic defects can be difficult, as a

Fig.9.16a,b. Polyostotic fibrous dysplasia in an adult female patient. Note typical ground glass lesions interspersed with sclerosis a in the distal humerus and proximal radius and ulna and b in the proximal femur. (From Sis-sons 1997)

Jaffe Lichtenstein Fibrous Dysplasia

Fig.9.16a,b. Polyostotic fibrous dysplasia in an adult female patient. Note typical ground glass lesions interspersed with sclerosis a in the distal humerus and proximal radius and ulna and b in the proximal femur. (From Sis-sons 1997)

disorder can exhibit either pattern of bone involvement and it is possible for both patterns to coexist in the same patient. As a consequence, a strict distinction is avoided in the following discussion, and the radiographic manifestations of any given disorder are detailed individually.

Fibrous dysplasia (Jaffe-Lichtenstein disease, OMIM 174800) manifests with solitary or multiple cyst-like lesions involving one bone (monostotic form, 7080%) or multiple bones (polyostotic form, 20-30%). In order of declining frequency, the sites of involvement for the monostotic form include one rib, femur, tibia, mandible, calvarium, and humerus. This form of disease is entirely asymptomatic unless an obvious pathologic fracture or an occult stress fracture develops (Nakashima et al. 1984). The polyostotic fibrous dysplasia most frequently involves the skull and facial bones, pelvis, spine, and shoulder girdle. An interesting feature is that involvement of the innominate bone is almost invariably associated with concomitant disease in the proximal portion of the femur (Gibson and Middlemiss 1971). Radiographical-ly, the disorder is characterized by well-defined, expansile areas of bone rarefaction interspersed with areas of reactive, patchy sclerosis (Fig. 9.16 a,b). The cyst-like, hazy or 'ground glass' appearance of the lesions, which in the tubular bones are intramedullary and predominantly diaphyseal in location, reflect the amount of fibro-osseous tissue that replaces normal bone. Degeneration and necrosis within the lesion may lead to focal, fluid-filled areas that appear markedly radiolucent, thereby mimicking a cystic lesion. Osteomalacia, limb deformity on weight-bearing, deficient bone modeling, pseudoarthrosis, multiple fractures, and limb leg discrepancy, are common manifestations of the polyostotic form of fibrous dysplasia. Single or multiple areas of radiolu-cency, reflecting accumulation of fibrous tissue within the bone ("brown tumors"), also occur in primary or secondary hyperparathyroidism (Brown et al. 1977). They are located preferentially at the level of the facial bones, pelvis, ribs, and femurs and may undergo necrotic liquefaction, producing cysts (Fig. 9.17 a,b). Resorption of bone, especially in the sub-periosteal location, is the cardinal radiographic manifestation of the disorder. Cystic angiomatosis of bone (hemangiomatosis or hemangiolymphangiomatosis, OMIM 123880) is a rare disorder characterized by multiple and widespread cyst-like lesions of the skeleton,frequently (in 70% of cases) associated with involvement of such organs as the liver, spleen, lungs, kidneys, lymph nodes, and peritoneal, pleural and pericardium membranes. Sporadic and familial cases have been described (Reid et al. 1989). Children and

Circumscribed Rarefaction

Fig. 9.17 a, b. Hyperparathyroidism. a In a 20-year-old subject affected by a dominantly inherited form of hyperparathy-roidism. Note well-circumscribed areas of radiolucency in the distal fibula. b In this 17-year-old sibling of the patient in a, multiple cyst-like lesions are seen in the pelvis and proximal femurs. (From Kozlowski et al. 1999)

Fig. 9.17 a, b. Hyperparathyroidism. a In a 20-year-old subject affected by a dominantly inherited form of hyperparathy-roidism. Note well-circumscribed areas of radiolucency in the distal fibula. b In this 17-year-old sibling of the patient in a, multiple cyst-like lesions are seen in the pelvis and proximal femurs. (From Kozlowski et al. 1999)

young adults are affected most commonly, and men are affected twice as often as women. The major clinical symptoms, including hepatosplenomegaly, anemia, congestive heart failure, respiratory compromise, ascites, and consumption coagulopathy, are related to the visceral involvement and are associated with a reduced life expectancy (Resnick et al. 1995; Waldron and Zeller 1969; Dadash-Zadeh and Schwartz 1976). In contrast, the skeletal involvement is clinically silent unless pathologic fractures develop. Roentgenographically, the lesions occur throughout the length of long bones and in the ribs, vertebrae, skull (Fig. 9.18), innominate bone, and clavicle, appearing as well-defined, round or ovoid intramedullary osteolytic areas surrounded by a thin sclerotic rim (Reid et al. 1989; Lomasney et al. 1996).Cor-tical violation and periostitis are uncommon. The dynamic characteristics of skeletal involvement, with lesion regression at one site and progression at another, have been emphasized by some investigators (Boyle 1972). Histologically, the lesions display numerous thin-walled vascular channels (cavernous or capillary-like vessels) lined with endothelial cells. Blood typically fills the hemangiomatous lesions, although the occurrence of lesions containing eosinophilic or proteinaceous fluid makes it impossible to differentiate between hemangioma and lymphan-gioma (Winterberger 1972). Indeed, lymphangiomas occur as a feature of cystic angiomatosis of bone. Despite the similarities of the pathologic substrate, cystic angiomatosis of bone is different from the massive osteolysis of Gorham (OMIM 123880),which appears to be nonmendelian. The radiographic appearance of cystic angiomatosis of bone can be very similar to that of polyostotic fibrous dysplasia, although the lesions are usually smaller and more circumscribed in cystic angiomatosis. The skeletal lesions seen in histiocytosis usually lack the peripheral rim of sclerosis and are not as numerous as those of cystic angiomatosis. In addition, localized pain and swelling are common in histiocytosis and rare in cystic angiomatosis of bone. Gross lucent defects located in the metaphyses, and related to the presence

Cystic Angiomatosis The Bone
Fig. 9.19. Membranous lipodystrophy in a 15-year-old girl. Note cyst-like bone lesions (arrow) in the distal ulnar metaph-ysis. (From Chaabane et al. 2000)

of fibrous cortical defects and nonossifying fibromas are typical manifestations of osteoglophonic dysplasia (OMIM 166250), a rhizomelic dwarfing disorder with severe facial abnormalities, craniostenosis, fibrous dysplasia of the mandible, and platyspondyly (Beighton 1989). Enchondromas are benign tumors composed of cartilage, often located in the hands, manifesting radiographically as central areas of bone rarefaction, with or without calcification, and scalloping of the endosteal margin of the cortex. Multiple enchondromas in the metaphyses and diaphyses of tubular bones, usually bilateral but asymmetrical, occur in enchondromatosis (Ollier disease, OMIM 166000), a nonfamilial disorder in which the development of the lesions is related to the persistence of islands of hyaline cartilage that alter normal growth of affected bones. These radiolucent masses of variable shape (elongated, oval or round) and size, often arranged in a fan-like appearance in the metaphyses, can cause considerable bone expansion, especially in the short tubular bones of the hands (Mainzer et al.

Fig. 9.20. Gaucher disease in a 31-year-old man. While the middle portion of the femoral shaft has retained its normal diameter, the proximal and distal portions show marked medullary expansion with cortical diminution. (From Hermann et al. 1997)

1971). Prominence of the soft tissues adjacent to the enchondromas is typical. Adjacent epiphyses are usually hypoplastic and irregular. Pathologic fractures may occur. The association of enchondromatosis and soft tissue cavernous hemangiomas substantiates the Maffucci syndrome (OMIM 166000) (Andren et al. 1963). The hemangiomas are detected at birth, and are variable in size and number. The distribution of the hemangiomas does not correlate with that of en-chondromas. The presence of soft tissue masses and phleboliths is a clue to the diagnosis of heman-giomas. Enchondroma-like lesions also occur in spondyloenchondromatosis (OMIM 271550), a rare disorder with short stature and severe platyspondyly (Schorr et al. 1976). Metachondromatosis (OMIM 156250), an autosomal dominant condition, is characterized by multiple cartilaginous exostoses and enchondromas with prominent marginal calcifications. The hands and feet are preferential sites of involvement, but virtually any bone may be affected. The exostoses differ from those occurring in the mul tiple hereditary exostoses syndrome in that they are smaller and point toward the physis - instead of the diaphysis - of the bone. The enchondromas occur in the iliac crests and metaphyseal regions of the tubular bones and appear as irregular, calcified lesions (Kennedy 1983; Lachman et al. 1974). Membranous lipodystrophy (presenile dementia with bone cysts, OMIM 221770), a disorder caused by loss-of-func-tion mutations in the DAP12 gene encoding tyrosine kinase-binding protein, is marked by multiple cystlike lesions of the skeleton appearing early in the disease course and resembling those of fibrous dysplasia and by prominent neuropsychiatric manifestations beginning in the fourth decade and progressing rapidly to total dementia (Hakola 1972; Akai et al. 1977; Araki et al. 1991). The pattern of bone involvement is characteristic,with multiple radiolucent lesions symmetrically distributed in the appendicular skeleton (the axial skeleton is distinctively spared) and involving the ends of long bones, phalanges, metacarpals, carpals, metatarsals, tarsals, and patella (Makela et al. 1982) (Fig. 9.19). The cysts are filled with a distinctive type of partly necrotic lipomembranous tissue. Fractures can occur after minor traumas (Verloes et al. 1997). Cystic transformation of bones, with a honeycomb appearance of coarse trabeculae, may be seen in those patients with osteogenesis imperfecta, type II (OMIM 166210,259400) who survive beyond infancy (Bauze et al. 1975). In Gaucher disease (OMIM 230800), a lysosomal storage disorder caused by the deficient activity of b-glucocerebrosidase, accumulation in the bone marrow of lipid-containing macrophages, the Gaucher cells, is associated with cellular necrosis, fibrous proliferation, resorption of the tra-becular bone, and bone marrow dysfunction with anemia and thrombocytopenia (Matsubara et al. 1982). The radiographic manifestations include either a pattern of diffusely increased bone radiolu-cency, medullary expansion, and cortical thinning (Fig. 9.20); or the presence of well-defined focal areas of radiolucency that sometimes simulate plasma cell myeloma, amyloidosis, and skeletal metastases (Watanabe et al. 1984; Tabas et al. 1986) (Fig. 9.21). The axial skeleton and proximal portions of the long bones are commonly involved. Vertebral collapses, pathologic fractures of the tubular bones, and is-chemic necrosis may complicate the course of the disease. Skeletal changes may be reversed by enzyme replacement therapy (Hermann et al. 1997). The skeletal manifestations of Niemann-Pick disease (OMIM 257250), another lipid-storage disease, are similar to those occurring in Gaucher disease except for a lower frequency of well-defined lytic lesions

Gaucher Syndrome
Fig. 9.21. Gaucher disease in a 12-year-old boy. Note large, cyst-like lesions in the mid-shaft of the right humerus, with endosteal scalloping. (From Hermann et al. 1997)

and absence of epiphyseal osteonecrosis (Resnick 1995). The intraosseous defects occasionally seen in neurofibromatosis type 1 (OMIM 162200), and commonly attributed to intraosseous neurofibromas, are controversial. Some cyst-like defects result from the incorporation of a subperiosteal hemorrhage (Fig. 9.22) or overgrowth of the periosteum around a previously external soft tissue lesion such as a neu-rofibroma. Others may merely represent artificial images caused by the oblique incidence of the X-ray beam on superficial depressions of the cortex. Multiple nonossifying fibromas appear to occur more frequently in neurofibromatosis patients than in the general population, possibly accounting for at least some of the radiolucent defects located at the periphery of the bone (Fig. 9.23 a,b) (Mandell et al. 1979). Whether or not intramedullary or intracorti-cal nerve fibers exist is debated (Feldman 1995). Multiple nonossifying fibromas (at least three) in association with extraskeletal anomalies such as cafe-au-lait spots, mental retardation, hypogonadism, cryptorchidism, eye anomalies, and cardiovascular malformations, confirm the diagnosis of Jaffe-Cam-panacci syndrome (Campanacci et al. 1983). The in-

Periosteal Hematoma
Fig. 9.22. Subperiosteal hematoma. There is elevation of a partially mineralized periosteum with minimal cortical erosion. (From Kenan et al. 1993)

dividual bone lesion, i.e., nonossifying fibroma or fibrous cortical defect, is a common benign lesion occurring in as many as 30 % of normal children over 2 years of age. In the majority of cases, a fibrous cortical defect resolves spontaneously, and only in a few cases does it enlarge, causing pathologic bone fractures (Blau et al. 1988). In Jaffe-Campanacci syndrome the nonossifying fibromas appear as multiple, large osteolytic lesions located eccentrically in the metaphysis and diaphysis of the long tubular bones. A link between this entity and neurofibromatosis is suggested by some investigators (Campanacci et al. 1983) and denied by others (Mirra et al. 1982). In tuberous sclerosis (OMIM 191100) the skeleton may be involved focally or diffusely with medullary or cortical, small, cyst-like radiolucent areas or dense sclerotic deposits (Fig. 9.24 a-c). Cortical lesions are most frequent in the short tubular bones of the hands and feet and include focal nodules, small round defects, marginal depressions, and cortical thickening (Teske et al. 1978). The intramedullary and intracortical radiolucent areas are believed to represent nonspecific fibrous tissue. Round, ovoid, or flame-shaped homogeneously dense sclerotic deposits in the spongy bone are also characteristic of

Nonossifying Fibroma Toe
Fig. 9.23 a,b. Neurofibromatosis in a 10-year-old boy. Note multiple, eccentrically located,well-defined radiolucent defects unassociated with periosteal reaction and reflecting nonossifying fibromas of a proximal femur and b distal femurs and proximal tibias

Fig. 9.24 a-c. Tuberous sclerosis in a 12-year-old boy. a, b Note small, ill-defined in-tramedullary areas of radio-lucency involving the phalanges of fingers and toes. c Anteroposterior view of the right ilium, showing an in-tramedullary osteosclerotic area with irregular, flame-shaped margins

Fig. 9.24 a-c. Tuberous sclerosis in a 12-year-old boy. a, b Note small, ill-defined in-tramedullary areas of radio-lucency involving the phalanges of fingers and toes. c Anteroposterior view of the right ilium, showing an in-tramedullary osteosclerotic area with irregular, flame-shaped margins

Tuberous Sclerosis Defects

the disorder and most typically involve the spine and pelvis (Green 1968). These lesions can enlarge slowly over a period of years, but do not expand the bone or progress beyond its contours. Localized areas of bone rarefaction, round or ovoid in shape and located centrally or eccentrically, can be observed in patients with sarcoidosis, a granulomatous disorder of unknown cause affecting multiple organ systems and manifesting principally with bilateral hilar adenopa-thy, pulmonary infiltrates, and skin and eye lesions. The bones are involved with a frequency varying from 1% to 13% (James et al. 1976), and usually only after other organs, specifically the lungs and skin, have been affected. The areas of bone rarefaction in sarcoidosis are most typically found in the middle and distal phalanges of the hands (Forouzesh et al. 1979; Lieberman and Krauthammer 1983). They are combined with alterations in the adjacent trabecular structure, which usually appears osteoporotic with a coarse or reticulated pattern and occasionally exhibits nodular or diffuse areas of sclerosis. At times, the pattern of osseous involvement is one of aggressive dissolution of bone, with cortical violation and sequestration. Interestingly, periostitis is distinctively unusual (Beasley et al. 1987). Single or multiple lyt-ic foci, often associated with cortical erosion, can be observed, albeit infrequently, in the long tubular bones, skull, ribs, pelvis, and spine. In the face, nasal bone dissolution is especially characteristic (Toomey and Bautista 1970; Zimmerman and Leeds 1976). In nevoid basal cell carcinoma syndrome (Gorlin syndrome, OMIM 109400) small, elongated (flame-shaped) multiple areas of radiolucency resembling those of sarcoidosis and tuberous sclerosis are characteristically seen in the phalanges, metacarpals, and carpals, although they can also involve the tubular bones of the arms, the femurs, and the ribs (Stroncek and Fonseca 1983). These pseudocystic lesions usually have an eccentric location and are occasionally combined with spotty deposits of calcium simulating osteopoikilosis (Novak and Bloss 1976; Blinder et al. 1984). Although these lesions have been related to intraosseous epithelial cysts, lipomas, or fibromas, which can occur in other locations in this syndrome, their pathogenesis remains unknown. True cysts lined with epithelium, follicular or dentigerous in type, do occur in the jaws as typical manifestations of this disorder. They appear as single or multiple, radi-olucent lesions with ill-defined margins varying in diameter from 1 cm to several centimeters. Symptoms related to these cysts include swelling, pain, and spontaneous drainage and may antedate the appearance of the skin lesions. Pathologic fracture, and occasionally the development of ameloblastoma are potential complications (Gorlin and Goltz 1960).

Single or multiple lytic lesions are cardinal manifestations in the Langerhans cell histiocytosis (histiocytosis X), a poorly defined group of disorders affecting predominantly children or young adults and characterized by histiocytic proliferation of tissues. Classically, three major forms are recognized: eosinophilic granuloma, Hand-Schüller-Christian disease, and Letterer-Siwe disease (OMIM 246400) (Lieberman et al. 1969; Schajowicz and Slullitel 1973). A considerable body of evidence suggests that these are intimately related entities and may in fact be different manifestations of the same condition, where eosinophilic granuloma is the mildest and commonest form, manifesting with single or multiple bone lesions; Hand-Schüller-Christian disease is a form manifesting with diabetes insipidus, exophthalmos, and chronic dissemination of osseous lesions; and Letterer-Siwe disease, the acute form, displays rapid dissemination of the histiocytic infiltrates in multiple visceral organs and has a poor prognosis (Chu et al. 1987). However, the nosology of the histiocytosis syndromes is still a subject of some debate (Egeler and d'Angio 1995). Significant fluctuations from one form to another have been observed (McCullough 1980). A specific type of histiocytic cell, the Langerhans cell, which contains cytoplasmic inclusion bodies (X bodies), is common to all types (Cutler and Krutchkoff 1977). The radiographic manifestations of individual lesions are similar for all forms and include a sharply defined osteolytic area with or without surrounding sclerosis (David et al. 1989). In the long bones, the lesions usually arise in the medullary cavity and subsequently extend to the cortex with endosteal erosion and periosteal re action. In the skull and pelvis the lytic lesions are usually particularly well circumscribed and occasionally exhibit a central focus of sclerosis termed a 'button' sequestrum (Fig. 9.25). These radiographic characteristics, together with the anatomic location of the osteolytic lesions, provide important clues to the diagnosis and allow for differentiation from other lytic conditions, such as infection, skeletal metas-tasis,leukemia, lymphoma, and Gaucher disease. Soft tissue masses can be present as well as the skeletal lesions. Pathologic fractures are common complications, especially in the ribs and spine. Spontaneous resolution of the osseous lesions can occur at any stage of the disease course, and healing is marked by sclerosis and cortical thickening. As anticipated, in eosinophilic granuloma the skeletal lesions are usually solitary initially and become multiple with time in only about 10% of the patients (Balducci et al. 1979). In Hand-Schüller-Christian disease the lytic lesions may be disseminated throughout the skeleton. In the skull, which is involved in the vast majority of cases, confluent lesions may isolate islands of bone, leading to the geographic appearance of the skull. 'Floating' teeth may be observed with a similar mechanism when the destructive process involves the mandible. In Letterer-Siwe disease, a disorder affecting predominantly children under 3 years of age, multiple bone lesions in the skull and facial bones are associated with a rapidly progressive clinical course, with fever, malaise, hepatosplenomegaly, lymphadenopathy, anemia, neutropenia, and throm-bocytopenia. Despite the clinical picture, the idea that the disease might be infectious has long been discredited (Christie et al. 1954). Familial cases of Letterer-Siwe disease have been reported (Freundlich et al. 1972; Frisell et al. 1977). Poorly defined areas of radiolucency of variable size, often localized in the spine and the metaphyseal/diaphyseal regions of the tubular bones, particularly the proximal femur and the distal humerus, can occur in amyloidosis, a group of disorders with amyloid deposition in several tissues and organs, including the heart, liver, kidney, spleen, skin, bone, and joints. The lytic lesions are often subcortical in location and produce scalloping of the adjacent cortex in a pattern that is not discernible from that caused by plasma cell myeloma (Weinfeld et al. 1970; Axelsson et al. 1970). In many instances, the bone abnormalities are the result of focal deposition of amyloid, although they may be linked with coexistent disease processes, notably plasma cell myeloma. Thus, radiographic differentiation between amyloidosis and plasma cell myeloma can be extremely difficult. Reactive sclerosis and

Non Langerhans Cell Histiocytosis

Fig. 9.25. Langerhans cell histiocytosis in a 1-year-old boy with a large osteolytic lesion of the proximal femur, containing a sclerotic focus or 'button' sequestrum (arrow), centrally. This is an unusual location for a button sequestrum, which is a lesion more commonly found in the skull. Subperiosteal new bone formation (open arrow) probably represents transcortical extension. (From Hindman et al. 1998)

Fig. 9.25. Langerhans cell histiocytosis in a 1-year-old boy with a large osteolytic lesion of the proximal femur, containing a sclerotic focus or 'button' sequestrum (arrow), centrally. This is an unusual location for a button sequestrum, which is a lesion more commonly found in the skull. Subperiosteal new bone formation (open arrow) probably represents transcortical extension. (From Hindman et al. 1998)

osteoporosis, sometimes complicated by pathologic fractures, are frequent associated manifestations, and the overall skeletal involvement simulates that of primary and metastatic skeletal neoplasms (Lai et al. 1984). In gout, the bony erosions produced by tophaceous deposits in the articular area can become sub-chondral in location and appear as radiolucent cystic areas apparently unrelated to the joint cavity (Cope et al. 1992). Farber lipogranulomatosis (Farber disease, OMIM 228000) is an autosomal recessive storage disease caused by an enzymatic defect in gly-colipid degradation resulting in accumulation of ceramide, and is characterized by subcutaneous nodules, arthritis, laryngeal involvement, hoarse cry, and severe psychomotor retardation manifesting in the first few weeks of life. Those affected are dead by 2 years of age,with a clinical course suggestive of malignant histiocytosis. The histological appearance is granulomatous (Abul-Haj et al. 1962; Antonarakis et al. 1984). A more benign clinical course, with longer survival and absence of any brain compromise, is also possible (Moser et al. 1989). In the bones, areas of radiolucency and erosion in the juxta-articular regions are observed (Sugita et al. 1972). The initial phase of Paget disease (OMIM 602080) is marked by intense osteoclastic resorption of the trabecular bone, which gives an 'osteolytic' appearance on radiograms. In the cranial vault, a level at which bone resorption is particularly common, the osteolytic changes go by the designation of osteoporosis cir-cumscripta. The diploe is enlarged, encroaching on the outer and inner table, and exhibits thin and sparse trabeculae, accounting for the increased radi-olucency. In the long bones, osteolysis begins almost invariably in the epiphysis and subsequently extends into the metaphysis and diaphysis with a V- or wedge-shaped front of radiolucency clearly demarcated from the adjacent unaffected bone. Involved bones are commonly enlarged, and fractures can occur after minor accidents. The initial osteolytic phase of Paget disease is followed by bone sclerosis and condensation, and often both manifestations coexist. Areas of bone sclerosis, cortical thickening, and coarsened trabeculae become prominent on radiograms.

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