Evaluation of Bone tumors with Magnetic Resonance Imaging and correlation with surgical and gross pathological findings.

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1 Evaluation of Bone tumors with Magnetic Resonance Imaging and correlation with surgical and gross pathological findings. S BAWEJA, R ARORA, S SINGH, A SHARMA, P NARANG, S GHUMAN, SK KAPOOR, S PURI Abstract Objectives: The purpose of this study is to evaluate the role of MRI in cases of bone tumors.to determine the MRI characteristics of different primary bone tumors.correlate and compare imaging findings with surgical and gross pathological findings whereever possible. Materials and methods: Twenty five patients (either suspected or proven cases of bone tumors) were included in this study.all patients were first evaluated with plain film examination. MRI was performed on a 1.5 Tesla Philips system (Gyroscan). Sequences and planes used were T1W and STIR sequence in coronal plane using body coil followed by T1W and T2W sequences in axial plane supplemented by sagittal and coronal planes using surface coil, second plane of imaging included STIR sequence and post contrast fat sat T1W images. Results : Sensitivity and specificity of MRI in detecting marrow involvement was 100%.MRI detected neurovascular bundle involvement with sensitivity, specificity, positive predictive value and negative predictive value of 100%, 92.8%, 75% and 100% respectively.mri detected joint involvement with sensitivity, specificity, positive predictive value and negative predictive value of 100%, 86%, 50% and 100% respectively.mri detected cortical break with sensitivity, specificity, positive predictive value and negative predictive value of 100%, 50%, 80% and 100% respectively. Although MRI could demonstrate different components of tumor, there was no difference in signal intensity patterns of different histological types of tumors. Conclusions : MRI is the preferred modality to image musculoskeletal tumors and should be obtained after radiographic evaluation. Its multiplanar imaging capability helps delineation of tumor and its extent in bone and soft tissues with high contrast resolution.it is an excellent modality to determine neurovascular bundle involvement,joint involvement,local extent and staging. Ind J Radiol Imag :4: Key words : Bone tumors,mri Introduction Evaluation of bone tumors involves a multimodality approach and whereas crosssectional imaging has extraordinarily improved the ability to characterize tumors,the differential diagnosis of primary osseous neoplasm remains based on their radiographic appearance.radiographs provide critical information regarding lesion location,margin,matrix mineralization,cortical involvement and adjacent periosteal reaction. But MRI is the best modality for focal extent and local staging.the excellent contrast resolution and multiplanar capabilities of MRI lead to improved evaluation of both intracompartmental and extracompartmental extent of bone This is particularly true with regards to invasion of muscle,neurovascular structures and adjacent fat planes and degree of marrow involvement. MRI has also been shown to be superior in assessing intraarticular extension and the presence of intratumoral necrosis and haemorrhage. MRI is the best technique to detect skip lesions (small metastasis separated from primary tumor by healthy tissue) which are often missed by other imaging means. MRI also plays an important role in evaluation of effectiveness and follow up of treatment.. In these days of managed care cross sectional imaging is limited to one modality and most centres will chose MRI in this From the Institution Department Of Radiology,G.B Pant Hospital And Maulana Azad Medical College,New Delhi Delhi University Request for Reprints:Saurabh Baweja, Address E 1/137 Arera Colony Bhopal,Mp,Pin Received 25 August 2005; Accepted 8 August 2006

2 S Baweja et al IJRI, 16:4, November 2006 regard1 Fig. 1 Coronal T1 W Image of Whole femur to demonstrate skip lesions in a case of osteosarcoma Fig.4 T1 and STIR coronal MR image of lower forearm and hand demonstrating invasion of joint in a case of giant cell tumor of radius. Fig.2, Axial MR Image demonstrating the tumor and the neurovascular bundle which is uninvolved by the tumor. Fig.5 Postcontrast T1W MR image of lower forearm and hand demonstrating invasion of joint in a case of giant cell tumor of radius. Fig.6 Plain X-ray (AP and Lateral) Showing osteosarcoma of upper part of Tibia Fig.3 Plain X-ray (AP and Lateral) Demonstrating giant cell tumor of lower end of radius. Materials and Methods This was a prospective study of 25 patients (either

3 613 IJRI, 16:4, November 2006 Evaluation of Bone tumors 613 suspected or proven cases of bone tumors) referred from orthopedics department. All patients were first evaluated with plain film examination.the plain film included atleast 2 projections. Fig.10 Coronal T2W MR image showing the extent of tumor in a case of multiple myeloma. Fig.7 STIR Coronal MR image of leg and knee demonstrating extent of marrow involvement in a case of osteosarcoma of tibia. Fig.11 Axial postcontrast T1W MR image showing encasement of axillary vessels by the tumor. Fig.8 Postcontrast T1 W image demonstrating the neurovascular bundle which is abutting the mass but is uninvolved in a case of osteosarcoma. Fig 9 Plain X-ray of arm and shoulder joint showing tumor of upper part of humerus with involvement of sixth rib ( a case of myeloma) Fig.12. Plain X-ray of pelvis showing chondrosarcoma of left ilium.

4 S Baweja et al IJRI, 16:4, November 2006 images were obtained after giving 10ml of IV Gadolinium in all cases. Results Age of the patients included in the study ranged from years with mean age years. Maximum number of patients in the study were in the age group years (10 patients). Minimum number of patients were in the above 40 years age group ( 3 patients ). Fig.13 Axial T1 and T2W MR image of pelvis demonstrating very high signal intensity of cartilaginous elements of tumor on T2W image in a case of chondrosarcoma. Out of 25 patients included in the study, 21 were males and 4 were females. 84% patients were males and 26% were females. Most common clinical presentation of patients was progressive swelling. Out of 25 patients included in the study 20 were malignant and 5 were benign.8 cases were of osteosarcoma,5 cases were of Ewing s sarcoma,4 were of chondrosarcoma,2 cases each of multiple myeloma and giant cell tumor, 1 case each of chordoma, aneurysmal bone cyst,osteochondroma and enchondroma. On plain film margins were illdefined in 16 cases, well defined in 5 cases and partly well defined in one case of malignant tumors. Margins were well defined in all five benign cases. The zone of transition was wide in 16 cases and narrow in 2 cases of malignant tumors.it was narrow in all 5 cases of benign tumors. On plain film cortical break was seen in 11 cases.it was not seen in 14 cases. Surgery could be performed in 18 of these cases. Fig.14 Axial T2W MR images demonstrating the neurovascular bundle which is uninvolved by the tumor in a case of osteosarcoma of femur. They then underwent MRI examination. Biopsy was done and finally treatment was planned. MRI was performed on a 1.5 Tesla Philips System (Gyroscan). Initially a large field of view T1W TSE and STIR TSE sequence was obtained of the area of interest in coronal plane using body coil to ensure that the extent of tumor and skip lesions were identified. This was followed by T1 and T2 weighted TSE sequences in axial plane supplemented by sagittal and coronal planes using surface coil. Second plane of imaging included a STIR sequence. Post contrast fat saturated T1 weighted SURGICAL/PATHOLOGICAL CORRELATION Cortical break PLAIN XRAY SURGICAL FINDINGS Present 8 cases 13 Absent 10 cases 5 Thus sensitivity, specificity,positive predictive value and negative predictive value of plain xray in detecting cortical break were 61.5%,100%,100% and 50% respectively. The soft tissue component was present in all cases except 2 cases of benign tumors. Periosteal reaction was present in 14 malignant cases.it

5 615 IJRI, 16:4, November 2006 was present in only one benign case out of 5 cases and absent in 6 malignant cases. Calcification or sclerosis was present in 15 malignant cases and 2 cases of benign tumors..it was absent in 5 malignant and 3 benign cases. MRI findings in bone tumours Marrow Involvement was seen in 24 out of 25 cases.one case of osteochondroma did not show marrow involvement on MRI which was confirmed on surgery.the extent of marrow involvement was best shown by T1W images and STIR coronal or sagittal sequence. It was confirmed by surgical and pathological findings in 18 cases. Soft tissue involvement was seen in 23 out of 25 cases. One case of osteochondroma and one case of Aneurysmal bone cyst did not show any obvious soft tissue component. Extra osseous involvement was best shown by T2W axial images. Joint involvement: Out of total 23 cases (2 cases joint involvement was not relevant) 6 cases showed evidence of joint involvement on MRI. The joint was uninvolved in 17 cases. Thus 23% cases demonstrated involvement of joint and 73.9% cases did not show joint involvement on MRI. Surgery could only be performed in 17 of these patients due to presence of metastasis in 7 patients. (2 cases with joint involvement and 5 cases without involvement on MRI could not be operated). MRI AND SURGICAL/ PATHOLOGIC CORRELATION ; Out of 17 patients in whom surgery was performed JOINT MRI FINDINGS SURGICOPATHOLOGIC INVOLVEMENT FINDINGS PRESENT 4/17 (23.5%) 2(11.7%) NOT PRESENT13/17 ( 76.4%) 15 (88.2%) The sensitiviy was 100%, specificity 86%, positive predictive value 50% and negative predictive value 100% Neurovascular bundle involvement: Out of a total of 24 cases, MRI showed neurovascular bundle involvement in 4 cases (all of which were malignant). It was uninvolved in 20 cases. Thus 16.6% cases demonstrated involvement of neurovascular bundle and 83.3% cases did not show involvement of neuro vascular bundle on MRI. Surgery could be performed in 17 of these patients. 7 patients could not be operated due to presence of metastasis. MRI and surgical/pathological correlation Out of 17 cases who were operated NEUROVASCULAR BUNDLE MRI FINDINGSSURGICALPATHOLOGICAL FINDINGS INVOLVED 4 /17 (23.5%) 3 /17(17.6%) UNINVOLVED 13 /17(76.4%) 14/17(82.3) One case shown to have involvement of neurovascular bundle on MRI but was uninvolved on surgery. Thus sensitivity in our study is 100%, specificity 92.8 %, positive predictive value 75% and negative predictive value 100%. Cortical break: Out of a total of 25 cases Cortical break was detected on MRI in 22 cases.it was absent in 3 cases. Thus 88% cases demonstrated cortical break and 12% % cases did not show cortical break on MRI. It is best demonstrated on T1 W images.18 cases were operated.7 cases were not operated due to presence of distant metastasis. Out of 18 cases operated cortical involvement was seen in 12 cases and it was absent in 6 cases. MRI and surgical/pathological correlation Out of 18 cases who were operated CORTICAL MRI FINDINGS SURGICAL FINDINGS INVOLVEMENT PRESENT 15/18(83.3%) 12/18 (66.66%) ABSENT 3/18 (16.6%) 6/18 ( 33.33%) The sensitivity,,specificity, positive predictive value and negative predictive value of MRI in detecting cortical involvement in our study are 100%, 50%, 80% and 100% respectively. Signal characteristics Most of the tumors were hypointense on T1W images and heterogenously hyperintense on T2W images. In general most tumors had a non specific appearance on MRI except for cartilaginous tumors.4 cases of chondrosarcoma were profoundly hyperintense on T2W images because of high water content of cartilaginous elements. Staging of tumors Enneking staging of malignant tumors was done.7 cases had distant metastasis (stage III).14 cases were of stage IIB.One case was in stage IIA STAGE III STAGE IIB STAGE II A 7 CASES 14 CASES 1 CASES Discussion Evaluation of Bone tumors 615 The imaging evaluation of bone tumors is critical because it helps distinguish malignant from benign lesions and guides the subsequent evaluation, therapy or observation of the patient.

6 S Baweja et al IJRI, 16:4, November 2006 MRI Findings Marrow involvement T1 weighted spin echo pulse sequence in a longitudinal (coronal or sagittal plane) was used for intramedullary staging.the low signal intensity of tumor on T1 weighted images was shown in sharp contrast with high signal intensity of fatty bone marrow. STIR sequence was also used to assess the extent of marrow involvement.fat signal is suppressed on STIR sequence appearing as a homogenous low signal intensity background. The tumor appears hyperintense on STIR images. In our study Marrow Involvement was seen in 24 out of 25 cases. marrow. It was confirmed by surgical and pathological findings in 18 cases. One case of osteochondroma did not show marrow involvement on MRI which was confirmed on surgery. The extent of marrow involvement was best shown by T1W images and STIR coronal or sagittal sequence. Ella Onikul2, David Parham et al in 1996 studied the accuracy of MR imaging for estimating imtraosseous extent of osteosarcoma. They compared how well T1W images and STIR images revealed the extent of longitudinal intraosseous involvement in osteosrcoma. R Golfieri et al3 in 1990 studied the role of STIR sequence in MRI examination of bone tumors and found that the STIR sequence suppressed the high signal from fatty bone marrow giving a clear depiction of tumor extent in its intramedullary component. Soft tissue component Soft tissue involvement was seen in 23 out of 25 cases. One case of osteochondroma and one case of aneurysmal bone cyst did not show any obvious soft tissue component. Extra osseous involvement was best shown by T2W axial images. Orest B Boyko and David A cory4 in 1986 evaluated 25 patients with osteogenic sarcoma and Ewings sarcoma with MRI and found that tumor involvement of the soft tissue is best shown by T2 weighted sequence. Cortical break Cortical break was detected on MRI in 22 cases.it was absent in 3 cases. It is best demonstrated on T1 longitudnal and T1 axial images.18 cases were operated. 7 cases could not be operated due to presence of distant metastasis. Out of 18 cases operated cortical involvement was seen in 12 cases and it was absent in 6 cases. The sensitivity, specificity, positive predictive value and negative predictive value of MRI in detecting cortical involvement in our study are 100%, 50%, 80% and 100% respectively. Joint Involvement: The presence or absence of joint involvement is particularly important in preoperative evaluation of tumor extent which will subsequently decide the appropriate surgical procedure (intra or extra articular resection. MRI is highly sensitive for detecting joint involvement in malignant tumors.however false positive diagnosis may lead to overstaging of tumor and result in unnecessarily radical surgical procedures.(wolfgang Schima 1994)5 We evaluated the relationship of the tumor to adjacent joint and involvement of the intrasynovial joint space was presumed where T1W images showed that a contrast enhancing mass extended into the joint space either by disruption of joint capsule or by intraarticular destruction of cortical bone and the articular cartilage, if present. Joint involvement was also presumed in cases of tumor extension into the cruciate ligaments which are intracapsular but extrasynovial. The presence of a joint effusion did not allow differentiation with regard to tumor extension into the joint. Only the absence of a joint effusion had a high predictive value for absence of joint involvement by tumor. Compared with unenhanced T1 weighted images, contrast enhanced T1 weighted images are more useful for assessing joint involvement. When MR imaging is used,the presence of peritumorous inflammatory changes may lead to false positive diagnosis of joint involvement,which may be followed by unnecessarily radical en bloc resection of joint.(schima 1994)5 In our study, MRI showed joint involvement in 6 cases.it was uninvolved in 17 cases. Surgery was performed in 18 patients due to presence of metastasis in others (one case joint involvement was not applicable) (2 cases with joint involvement and 5 cases without involvement on MRI could not be operated). On operative findings it was found that 2 cases had involvement of joint and in 15 cases the joint was uninvolved. In 2 cases MRI gave false positive results. The sensitivity 100%,specificity 86%, positive predictive value 50% and negative predictive value 100% respectively The results in our study are quite similar to Van Trommel et al6 who found sensitivity specificity positive predictive value and negative predictive value to be 100%, 70, 86.4% and 100% respectively. Neurovascular Bundle Involvement : Radiologic depiction of soft tissue mass with respect to neurovascular bundle is important in planning surgical approaches for local tumor control. Tumor with deviation of neurovascular bundle may be considered for amputation instead of a limb salvage procedure because the ability to obtain adequate surgical margins around the tumor

7 617 IJRI, 16:4, November 2006 may be compromised. On MRI involvement of neurovascular bundle was present when tumor is surrounding these structures or containing atleast one half the circumference and obliterating the associated fat plane. The relationship of NV bundle to the tumor was best shown on T2W axial images and T1W post contrast axial sections. Fat saturated T1 weighted post contrast images are superior to T2 weighted images in defining the proximity of soft tissue tumor mass to neurovascular bundle Suzanne,William Kaufman7 in 1997 found that it is easier to evaluate neurovascular bundle proximity to tumor with Fat sat T1 W post contrast images than with T2W for 64% of cases. In our study MRI showed neurovascular bundle involvement in 4 cases (all of which were malignant).it was uninvolved in 20 cases. Surgery could be performed in 18 of these patients (in one case neurovascular bundle involvement was not applicable). 7 patients could not be operated due to presence of metastasis. One case was detected false positive on MRI. Thus sensitivity in our study is 100%, specificity 92.8 %, positive predictive value 75% and negative predictive value 100%. Result in our study is comparable to Bloem JL et al8 who found sensitivity, specificity, positive predictive value and negative predictive value to be 100%, 98%, 98% and 100% respectively.the positive predictive value is higher as compared to our study because smaller number of patients in our study showed neurovascular bundle involvement on MRI. Signal Intensity Pattern: Despite great value of MR imaging in the staging of bone lesions, it is of relatively little value in specific histological diagnosis. There are specific diagnoses however that have a relatively characteristic MR appearance. Cohen et al9 observed a distinctive MR appearance in chondroid lesions containing a matrix of hyaline cartilage.the unique pattern consisted of homogenous high signal in a discernible lobular configuration on T2 weighted spin echo images. This MR appearance reflects underlying high ratio of water content to mucopolysaccharide component within hyaline cartilage. MR imaging also allows precise measurement of thickness of cartilage cap of an osteochondroma. It is agreed that the risk of malignant transformation is directly related to thickness of cartilage cap especially when later exceeds 2 cm. In our study, 5 cases of cartilaginous tumors were correctly characterized with MRI (4 cases of chondrosarcoma and one case of enchondroma). They were profoundly hyperintense on T2W images because of high water content of cartilaginous elements. We demonstrated cartilage cap and determined its thickness in one case of osteochondroma and found its thickness was less than 1 cm thus ruling out malignancy. Rest of the tumors had a non specific appearance on MRI. Staging of tumors Enneking9 staging of malignant tumors was done.7 cases had distant metastasis (stage III). 14 cases were of stage IIB.One case was in stage IIA STAGE III STAGE IIB STAGE II A 7 CASES 14 CASES 1 CASES Conclusion: Conventional radiography is the first line of diagnosis for bone tumors. The radiograph can localize the lesion and determine its degree of aggressiveness enabling the radiologist to make an informed differential diagnosis and in many cases a specific diagnosis. MRI is the preferred modality to image musculoskeletal tumors and should be obtained after radiographic evaluation. Its multiplanar imaging capability helps delineation of tumor and its extent in bone and soft tissues with high contrast resolution. MRI is an excellent modality to demonstrate marrow involvement by the tumor,involvement of neurovascular bundle and joint invasion. MRI can demonstrate cortical breach but false positive results may occur if cortex is markedly thinned out. MRI is the modality of choice for local extent and tumor staging Bibliography Evaluation of Bone tumors George C Nomikos, Mark D Murphey, Primary Bone tumors of lower extremities Radiologic clinics of North America 2002 ;40: Ella Onikul, Barry D Fletcher Accuracy of MR imaging for estimating intraosseous extent of osteosarcoma AJR November 1996;167 : R Golfieri, H Baddeley. The role of STIR sequence in magnetic resonance imaging examination of bone tumors BJR,1990,63 ; Orest Boyko, David A Cory MR Imaging of osteosarcoma and Ewings Sarcoma AJR Feb 1987; 148 : Wolfgang Schima, Gabriele Amann Preoperative staging of osteosarcoma Efficacy of MR imaging in detecting joint involvement AJR 1994 ;163 : Michiel F Van Trommel, Herman M Kroon, MR imaging based strategies in limb salvage surgery for osteosarcoma of the distal femur, Skeletal Radiology 1997;26: Suzanne A Gronemeyer, William M Kauffman Fat saturated contrast enhanced T1 weighted MRI in evaluation of osteosarcoma and Ewings sarcoma, Journal magnetic resonance imaging 1997;7: JL Bloem, HJ vander woude, Does magnetic resonance imaging make a difference for patients with musculoskeletal sarcoma? The British Journal of Radiology 1997 ;70: Thomas H Berquist, Magnetic resonance Imaging of Primary skeletal neoplasms, Radiologic clinics of North

8 S Baweja et al IJRI, 16:4, November 2006 America March ;2 : George C Nomikos,Mark D Murphey,Primary Bone tumors of lower extremities Radiologic clinics of North America 2002;40: