Myositis ossificans: Spectrum of imaging findings and pathologic correlation

Transcription

1 Myositis ossificans: Spectrum of imaging findings and pathologic correlation Poster No.: C-2326 Congress: ECR 2010 Type: Educational Exhibit Topic: Musculoskeletal Authors: C. Gonzalez-Junyent, M. M. Menso, J. E. Otero Ruiz, I. Corcuera, J. Llauger, J. Palmer, S. Bague; Barcelona/ES Keywords: Myositis ossificans, Musculoskeletal radiology, pseudotumors DOI: /ecr2010/C-2326 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 26

2 Learning objectives 1. To review the clinicopathologic spectrum of myositis ossificans. 2. To discuss different presentations, imaging characteristics, biopsy considerations, and pathologic appearances of myositis ossificans. 3. To educate the viewer to assure accurate diagnosis of this pseudotumoral lesion. Background Myositis ossificans (MO) is a benign, solitary, self-limiting soft tissue lesion characterized by heterotopic bone and cartilage formation. MO usually occurs within a muscle (Fig. 1) on page 3, although it may also occur around ligaments, tendons, aponeurosis, and joint capsules. About 80% of cases of MO arise in the large muscles of the extremities. Microscopically, lesions have three components: a central zone of proliferating fibroblasts, a middle zone that contains osteoblasts and foci of inmature bone (Fig. 2) on page 4 and a peripheral layer with mature bone trabeculae (Fig. 3). on page 5 MO is most common in young adults and is quite rare in children (Fig. 4 on page 5,5 on page,6 on page 7,7) on page 8. The most common signs and symptoms are pain, tenderness, and soft tissue swelling. Some lesions are asymptomatic and incidentally discovered during radiologic examinations. Page 2 of 26

3 The pathogenesis of MO is unknown. An association with trauma is seen in less than 20% of cases. It is not a true neoplasm or a premalignant lesion, and there is no evidence that such lesions may undergo malignant transformation. Local excision is generally curative. However, the radiologist should be sufficiently familiar with the clinical and radiologic manifestations of the disease to report the correct diagnosis and be able to direct management to prevent unnecessary interventions. Recognition of the characteristic imaging findings of MO makes it possible to achieve a successful presumptive diagnosis and to differentiate it from other mineralized soft tissue lesions, specially extraskeletal and juxtacortical osteosarcoma. Images for this section: Page 3 of 26

4 Fig. 1: Photomicrograph (H-E satin): Note sharp delineation of outer surface from surrounding soft tissue. Fibrosis and atrophy of adjacent muscle are seen. Page 4 of 26

5 Fig. 2: Photomicrograph (H-E stain):left: Central nonossified part of lesion is composed of loose fibroblastic tissue. RIGHT: Early phases of peripheral heterotopic ossification with bone trabeculae with prominent osteoblastic rimming. Fig. 3: Photomicrograph (H-E stain) shows a mature, well-developed shell of bone delineating the periphery of the lesion. Page 5 of 26

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7 Fig. 4: Spine radiograph in a 10-years-old girl with history of 2 weeks of back pain.the plain film was normal. Because the pain persist a MRI study was performed(figures 2 and 3). Fig. 5: Early stage of myositis ossificans.coronal MR SPIR T2-weighted images show a mass demonstrating a signal intesity greater than that on fat with extens surrounding edema. In the center of the lesion there are areas with increased signal intensity probably related to the extremely celular areas of proliferating fibroblast and myofibroblasts within a myxoid stroma or extracellular matrix. MR images after intravenous contrast media administratin were also performed. (see figure 5). Page 7 of 26

8 Fig. 6: Axial MR images on T1WI after intravenous contrast administration show a nodular lesion with enhancement on the right paravertebral musculature within the body of D9. The main diagnose after analysing all the MRI study was myositis ossificans. Because it is a quite rare entity in children a CT and a biopsy were done to assure the diagnose. Page 8 of 26

9 Fig. 7: CT scan + biopsy (soft tissue window) shows a well-defined mass with distinct bony character, with more mature bone appearing in the periphery of the mass.the calcification was not seen on the radiographs performed 3 weeks before. After pathologic study the diagnose was myositis ossificans. Page 9 of 26

10 Imaging findings OR Procedure details We retrospectively reviewed our radiologic and pathologic files to identify patients with myositis ossificans. Fourteen patients with pathologically -proven diagnosis underwent radiologic examination, CT, or MR imaging. Each lesion was evaluated for location, size, pattern of calcification, overall signal intensity (relative to muscle), enhancement characteristics, and evolutive changes. Radiologic diagnosis of myositis ossificans is based on plain radiographs, CT, and MRI. Plain films Radiographs reveal a soft tissue mass with faint calcification as early as in 2 weeks of the onset of symptoms (Fig.1) on page 12. A well-circumscribed mass is almost always apparent by 6-8 weeks (Fig.2) on page 12. Posteriorly, this lesion becomes smaller. Computed Tomography On CT images, myositis ossificans shows characteristic findings consisting of peripherally mineralized intramuscular mass (Fig.3) on page 14. The center of the mass has decreased attenuation. Mature lesions may show diffuse ossification. Surrounding edema could be seen but it is best appreciate on MR images (Fig. 4) on page 14. Magnetic Resonance Image There are three lesions stages and MRI appeareance depends on the age of injury, maturity of ossification, extent of mionecrosis and degree of inflammatory reaction. On early stages, when mineralization is not yet visible on plain films, lesions demonstrate high signal intensity (greater than that of fat) on T2-weighted images. Lesions are moderately inhomogeneous and are associated with diffuse surrounding edema. On T1weighted images, lesions are isointense relative to skeletal muscle, with poorly defined margins. It may exist a surrounding line of decreased signal intensity that indicates peripheral mineralization. In relation with the highly cellular central areas of proliferating fibroblast and myofibroblasts within mixoid stroma, areas of increased signal intensity on T2-weighted images may be seen (Fig. 5 on page 15 on page 15,6) on page 16. On intermediate stages, lesions have a similar appearance, but demonstrates the typical curvilinear, low-intensity rim corresponding to peripheral calcification (Fig. 7) on page 17. Fluid-fluid levels can also be seen due to previous hemorrhage, which is not an uncommon histologic finding in the inner portion of the lesion (Fig. 8) on page 19. Page 10 of 26

11 On the late stage, lesions are inhomogeneous, well-defined masses with signal intensity similar to that of fat on both T1WI and T2WI, without associated edema (Fig. 9) on page 19. On spin-echo sequences, it can also be seen a relative decrease signal intensity secondary to ossification and fibrosis. Inhomogeneous areas of intermediate signal intensity on T2WI and high intensity on T1WI are related to the presence of mature fat between bone trabeculae. Areas of decreased signal intensity on both T1WI and T2WI may be secondary to hemosiderin deposition and fibrosis. Active lesions show enhancement after intravenous contrast media administration. It can also be seen enhancement surrounding the lesions which reflects the edema associated (Fig. 10). on page 20 Scintigraphy This technique shows an intense focal tracer accumulation on both flow and blood pool images (Fig. 11) on page 21. This imaging tool is useful to evaluate the activity which is important because when activity is reduced, the ossification is judged to be mature and surgery may performed with a low risk of recurrence. Page 11 of 26

12 Images for this section: Fig. 1: Anteroposterior and lateral radiographs of the right knee show a lateral soft tissue lesion with faint floccular densities. Page 12 of 26

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14 Fig. 2: Evolution of myositis ossificans by plain films. (a)ap radiograph shows a slight calcification in the soft tissue next to the shoulder blade.(b)the radiograph perform 3 weeks later shows better defined soft tissue mass with faint irregular floccular densities. (c)after 6 weeks the plain film showed a well-circumscribed mass with a distinct bony character, with more mature bone appearing in the periphery of the mass.(d)after 2 months without treatment the well-defined mass became smaller and with diffuse calcification. Fig. 3: Axial CT scan (soft tissue window) shows a well-circumscribed intramuscular mass with rim mineralization. Page 14 of 26

15 Fig. 4: (A) Axial CT demostrates the characteristic peripheral mineralization of myositis ossificans.no surrounding edema is apreciated. (B) MR Fat-suppressed T1WI after intravenous gadolinium administration shows an important intramuscular edema. Page 15 of 26

16 Fig. 5: Early stage of myositis ossificans.coronal MR SPIR T2-weighted images show a mass demonstrating a signal intesity greater than that on fat with extens surrounding edema. In the center of the lesion there are areas with increased signal intensity probably related to the extremely celular areas of proliferating fibroblast and myofibroblasts within a myxoid stroma or extracellular matrix. MR images after intravenous contrast media administratin were also performed. (see figure 5). Page 16 of 26

17 Fig. 6: Early stage of myositis ossificans. Sagital MR contrast-enhanced fat-supressed T1-weighted images shows a nodular lesion with inhomogeneous enhancement in the supraspinatus muscle. Enhancement surrounding the lesion is also apreciated reflecting the soft-tissue edema. Page 17 of 26

18 Fig. 7: Intermediate stage of myositis ossificans of the right tight in a 13-years-old boy.(a)anteroposterior radiograph of the right tight shows a well-defined osseus mass. (b)coronal STIR MR image shows an homogeneous increased signal intensity wellcircumscribed mass with peripheral low signal intensity due to the calcification and a extensal surrounding area of high signal intensity that reflects the asssociated edema. Page 18 of 26

19 (c)axial MR T1WI of the right tight shows a isointense signal mass relative to the skeletal muscle with poorly defined margins demonstrating a decreased signal intensity.(d)axial T2WI of the right tight shows a high signal intensity well-defined mass with peripheral mineralization and a surrounding area of increased signal intesity reflecting the edema associated. Fig. 8: Axial MR T1WI shows a well-defined inhomegeneous mass in the left latissimus dorsi muscle with fluid-fluid level indicating hemorrhage into the mass. Page 19 of 26

20 Fig. 9: Mature stage of myositis ossificans. Axial MR T2WI only demostrates the peripheral hyposignal reflecting the mineralization without any surrounding edema. Page 20 of 26

21 Fig. 10: Myositis ossificans localized on the vastus lateralis of the quadriceps.(a) Axial MR T1WI shows a slightly hypointense nodular lesion relative to the skeletal muscle. (B) Axial MR T1WI after intravenous contrast administration shows the same lesion with inhomogeneous enhacement and areas of decreased intensity in the center of the lesion. (C) Axial MR SPIR weigthed images shows the nodular lesion with high signal intensity and intramuscular edema. Page 21 of 26

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23 Fig. 11: Scintigraphy shows an intense tracer accumulation next to the distal femoral diaphysis in the blood pool phase indicating great activity. Page 23 of 26

24 Conclusion Myositis ossificans is a benign reactive heterotopic formation of fibrous tissue, cartilage, and bone within skeletal muscle. The radiologic findings in plain film, CT or MRI are characteristic to suggest a specific diagnosis. However, in early stages this entity can mimic a malignant tumor and to avoid unnecessary invasive procedures it is important to do an accurate diagnosis. Personal Information 1.Carla Gonzalez-Junyent, MD. Radiologist in training. Hospital de la Santa Creu i Sant Pau, Barcelona. SPAIN. cgonzalezj@santpau.cat 2. Maria Magdalena Menso, MD. Radiologist in training. Hospital de la Santa Creu i Sant Pau, Barcelona. SPAIN. mmenso@santpau.cat 3. Jorge Enrique Otero Ruiz, MD. Radiologist in training. Hospital de la Santa Creu i Sant Pau, Barcelona. SPAIN. Page 24 of 26

25 4. Idoia Corcuera Solano, MD. Radiologist in training. Hospital de la Santa Creu i Sant Pau, Barcelona. SPAIN. icorcuera@santpa.cat 5. Jaume Llauger, MD. Radiologist. Hospital de la Santa Creu i Sant Pau, Barcelona. SPAIN. jllauger@santpau.cat 6. Jaume Palmer, MD. Radiologist. Hospital de la Santa Creu i Sant Pau, Barcelona. SPAIN. jpalmer@santpau.cat 7. Silvia Bague, MD. Pathologist. Hospital de la Santa Creu i Sant Pau, Barcelona. SPAIN. Sbaguer@santpau.cat References 1. Eoghan E. Laffan,Bo-Yee Ngan and Oscar M. Navarro. Pediatric Soft-Tissue Tumors and Pseudotumors: MR Imaging Features with Pathologic Correlation: Part 2. Tumors of Fibroblastic/Myofibroblastic, So-called Fibrohistiocytic, Muscular, Lymphomatous, Neurogenic, Hair Matrix, and Uncertain Origin Radiographics 2009; 29:e Jim S. Wu and Mary G. Hochman. Soft-Tissue Tumors and Tumorlike Lesions: A Systematic Imaging Approach. Radiology 2009;253: M J Kransdorf and J M Meis. From the archives of the AFIP. Extraskeletal osseous and cartilaginous tumors of the extremities. Radiographics 1993;13: Page 25 of 26

26 4. Gregory Scott Stacy and Larry B. Dixon. Pitfalls in MR Image Interpretation Prompting Referrals to an Orthopedic Oncology Clinic. Radiographics 2007;27: Kathryn M. Olsen and Felix S. Chew. Tumoral Calcinosis: Pearls, Polemics, and Alternative Possibilities. Radiographics 2006;26: William E. Palmer, Sharon J. Kuong, Hany M. Elmadbouh. MR Imaging of Myotendinous Strain. AJR Am J Roentgenol 1999;173: Jay P. Heiken,Joseph K. T. Lee, Ralph L. Smathers, William G. Totty, William A. Murphy. CT of Benign Soft-Tissue Masses of the Extremities.AJR Am J Roentgenol 1984;142: Page 26 of 26