1. ECR 2010. March 4-8, Vienna/Austria. María Jesús Adán Martín, MD. Yolanda Herrero Gómez,MD. Vivian Artiles Valle, MD. Mar Céspedes Más, MD. Soledad Fernández Zapardiel, MD. Alejandro Pérez Martínez, MD. Rocío González Tovar, MD. Raquel Moreno de la Presa, MD. Hospital Virgen de la Salud. Toledo.Spain.

2.  1.-To describe the physiopathology of fibrous dysplasia (FD) lesions and correlate them with the imaging findings.  2.-To illustrate the broad spectrum of radiological imaging features of this entity, in both its monostotic and polyostotic forms, using a multimodality approach with conventional radiography (CR), computed tomography (CT) and magnetic resonance (MR) and its distribution pattern.  3.-To discuss the most likely differential diagnoses of this disease for each location.  4.-To provide key points in order to avoid unnecessary examinations

3. INRODUCTION AND CLINICAL FINDINGS. INRODUCTION AND CLINICAL FINDINGS.  FD is a non-herited developmental anomaly in which the normal medullary space of the affected bone is replaced by fibroosseous tissue. It is a relatively common benign skeletal disorder that is typically encountered in adolescents and young adults, (first to second decades), and it may affect one or multiple bones (monostotic or polyostotic fibrous dysplasia (MFD and PFD respectively).  Although some patients with uncomplicated monostotic lesions may report non-specific symptoms, most of them are asymptomatic.As these lesions do not cause significant deformity, this entity is mostly diagnosed incidentally when patients undergo examinations for other conditions. As a rule, they do not convert to the polyostotic form, do not increase in size and become inactive at puberty.  However, it may be complicated by pathological fractures and, rarely, by malignant degeneration.  It can also be associated with aneurysmal bone cysts.  The polyostotic variety is more severe. It results in significant deformities and, although the lesions become quiescent after puberty, the deformities may progress.

4.  From one-third to one-half of patients affected with polyostotic fibrous dysplasia (PFD) present yellowish or brownish non-elevated patches of cutaneous pigmentation (cafe-au-lait spots), situated predominantly on the trunk.The borders of these dermatologic lesions are typically inregular in contrast to the regular margins observed in the cafe-au-lait spots of patients afflicted with neurofibromatosis.  Multiple endocrine disorders have been described in association with fibrous dysplasia. Of these, the best known is McCune-Albright syndrome, which consists of the triad of polyostotic fibrous dysplasia (typically unilateral), cutaneous cafe-au-taft spots (usually ipsilateral to the bone lesions), and endocrine dysfunction(especially precocious puberty in girls).Manifestation of the complete triad is rare, however.  Fibrous dysplasia has also been reported in association with other endocrine dysfunctions, such as hyperthyroidism, hyperparathynoidism, acromegaly, diabetes mellitus, and Cushing syndrome.It also occurs as a component of Mazabraud’s syndrome (intramuscular myxoma associated with FD).  Although cherubism has been described as a subtype of FD, specially a hereditary craniofacial FD due to similar radiological appearances, recent genetic analysis show them to be separate entities.

5.  We undertook a retrospective review of all FD lesions diagnosed at our hospital.  Radiographic appearances of fibrous dysplasia are usually diagnostic. CR is the first technique used in most cases Atypical locations and radiological appearances were studied with CT and MR.  This condition has well documented radiographic, scintigraphic and CT findings. The MRI appearances of this condition have not been widely published.

6.  Radiographs show lesions that are medullary in origin. Sometimes, the lesions may be eccentric in location (corticomedullary distribution).  The lesion affects typically to methaphys or both metaphysis and diaphysis and rarely extends into the epiphysis in the immature skeleton, but may extend to the end of the bone after physeal closure.  Replacement of normal cancellous bone with abnormal tissue (woven bone) produces a purely lytic or denser lesion with a typical greyish ground-glass appearance.The lesions are usually bound by a characteristic thick layer of reactive bone that has been described as a ‘‘rind’’.  Fibrous dysplasia often causes scalloping of the endosteum. Bony expansion is common. The lesions are typically sharply marginated. Focal nodules of cartilage can produce foci of ‘‘pop-corn’’ like calcification. If the lesion contains a large amount of cartilaginous tissue, the calcification may be denser with a ‘‘cloud of smoke’’ appearance.  Radiographic appearances of fibrous dysplasia are usually diagnostic. In equivocal cases, histopathological correlation may be required. 3.1-RADIOGRAPHIC AND CT FEATURES.

7.  Most of the lesions are largely isointense to skeletal muscle on T1 weighted images.On T2 weighted images, lesions are typically heterogeneously hyperintense with hypointense, isointense or markedly hyperintense areas within.  In some cases,lesions can be homogeneous on both T1 and T2 weighted images  Depending on the appearance on both the T1 and T2 weighted images, the heterogeneous areas may be due to calcification, cystic changes, fatty areas,or septations.  The enhancement pattern of fibrous dysplasia is variable and can be categorized as: patchy central enhancement, rim enhancement, homogeneous enhancement or a combination.  On both T1 and T2 weighted images, an outer hypointense rim was typically seen and corresponded to the sclerotic rind seen on radiographs 3.2- MAGNETIC RESONANCE IMAGING FINDINGS

8. BENIGN FIBROUS BONE LESIONS (adapted from reference 3) MALIGNANT

9. DISTRIBUTION OF FD LESIONS Now,Lets go for a few cases… 20% 2% 30% 1% 5% 1% 25% 2% 5% 8% Adaptated from reference 1 3%

10. a Fig.2. Computed tomographic (CT) scan (b) axial and (c and d) coronal and sagittal reformatted CT images (b) confirmed the existence of a subcortical lytic lesion surrounded by a sclerotic thick ring in proximal diaphysis of left femur next to greater trochanter (arrows) consistent with fibrous dysplasia.Note a perfect correlation with conventional radiography (CR). a d b c TEACH POINT TO TAKE HOME. Lesion geographic pattern (1A) indicates its little agressive nature. Femur, is the most common affected long bone in monostotic fibrous dysplasia. DIFFERENTIAL DIAGNOSIS: Non ossifying fibroma.

11. Fig.3. Fibular cystic fibrous dysplasia.57 year-old man with knee bilateral pain.a).Posteroanterior weight bearing radiograph shows a subtle lytic lesion in proximal ephysis of fibula (*).(b) Coronal spin eco T1-weighted MR image depicts a well- defined hypointense and homogeneous medullary mass extending into diaphysis and proximal epiphysis of right fibula (white arrow).Coronal (c) and sagittal (d) fast spin-echo T2-weighted MR images with fat-suppression shows the predominantly high-signal-intensity of the mass with multiloculated appearance (arrows) consistent with cystic fibrous dysplasia.MR determined real extension of the lesion. a b c d

12. Fig 4.- Cranial polyostotic fibrous dysplasia. 17 year-old man with selected pain in right malar bone. Radiographs (a) and (b) show a mixed and expansile lesion in right temporal bone. Axial (c and d), and sagittal reformated (e) CT scans confirmed marked, expansile osseous remodeling with a ground-glass appearance (arrow) in the temporal and sphenoid bones. D

13. Figure 5A. 23 year-old woman who suffered ovarian torsion. During her stay in the hospital a chest X ray was realized demostrated lytic lesions with ground-glass appearance in both humerus. Anteroposterior radiographs (on the left and middle) of both humerus and CT scancoronal reformated CT image, on the right ),were realized to confirm it.

14. D Fig 5B.The same patient that 5A. Anteroposterior both forearms and lateral left forearm radiographs show similar lesions in dyafisis of left radium, right second and left first metacarpians.The.radiological findings are consistent with polyostotic fibrous dysplasia.

15. f Figure 7.Coronal (c an d) and sagittal (e and f) reformated CT images.Coronal reformated CT scan with soft tissue window ( c) ilustrate a small kidneys in relation with cronic renal disease..On the rigt sagital reformated CT images with bone window show the rib lytic lesion.Bottom,coronal (e ) an sagital reformated CT images show difusse increased of density of vertebral bodies of spine.All these findings are compatible with renal osteodystrophy.The final diagnoses for rib lesion in this way was brown tumor in the setting of secondary hyperparathyroidms due to cronic renal disease ( membranoproliferative type I glomerulonephritis). d c e Figure 6. 30 year-old woman with shoulder pain.No other clinical dates were reported. Anteroposterior y axial radiographs of right shoulder show an expansive lytic lesion at posterior arc of fourth rib (arrows in a and b). The differential diagnoses in this case is large( (click to check list). Radiologist recomended correlation with clinical history and realize a thoracic and abdominopelvic CT (click to view it) to exclude metastasic origin. DIFFERENTIAL DIAGNOSIS ( IN ORDER FROM THE MOST TO THE LEAST PROBABLE ) 1.-Monostotic fibrous dysplasia. 2.-Brown tumor (hyperparathyroidsm). 3.Metastasis. 4.Myeloma.