Radioimaging Evaluation of Primary Bone Tumors and Tumor like Lesions

Background: Bone tumour is relatively rarely encountered by radiologist, so sometimes it creates diagnostic difficulty. Aim over study was   to determine the X-ray CT and MRI characteristics of different primary bone tumours and tumour like lesion and correlation of radiologic diagnosis with histopathologic diagnosis whenever possible. To understand the advantages and limitations of different radio-imaging techniques. Subjects and Methods: We have studied total 45 cases of primary bone tumour and tumour like lesions during study of 15 months duration in department of Radiodiagnosis, Baroda Medical College, Vadodara, Gujarat, India. First radiological diagnosis and differential diagnosis was given than histopathologic examination was done in all malignant and indeterminate lesions for final diagnosis. Results:  Out of 45 patients   21 (46.6%) were female and 24 (53.3%) were male. Benign and malignant lesions were 69% and 31% respectively. Multiple lesions were common with osteochondroma, hemangioma and multiple myeloma. Most common malignant tumour was osteosarcoma and benign tumour was osteochondroma. Pathologic fracture was seen in 6 patients but out of them 2 fractures were missed on radiograph. Skip lesions were seen in two malignant lesions which was missed on radiograph and CT but it was easily detected on MRI. Conclusion: Radiography is baseline investigation for evaluation of bone tumor and tumour like lesions. Pathological fracture and matrix mineralization can be better seen on CT. MR is superior in detection skip lesion, soft tissue and marrow extension.


Introduction
The development of more effective chemotherapeutic agents, combined with improvements in limb salvage surgery and advances in imaging technology, has resulted in improved staging and ultimate outcome in patients with these bone and soft-tissue lesions.
Plain radiographs are an indispensable part of the diagnostic evaluation of the patients with any skeletal symptoms and signs, and remains the first and foremost imaging modality. Plain radiograph is a cheap, sensitive and easily available imaging tool and has high cost-benefit ratio.
However, plain radiograph is a two dimensional representation of a three dimensional body part; and hence carries inherently low spatial resolution and overlapping of structures. Moreover, plain radiograph has limited role in evaluation of the marrow and soft tissues, for which CT scan and preferably MRI are more advantageous.
In current scenario, Patient with skeletomuscular symptoms, the provisional diagnosis regarding the presence and type of the bone tumour is usually made by a plain radiograph. For further characterization and extension of the lesion CT scan or MRI is used.
Radiology provides the idea about the gross pathoanatomy about the lesion, whereas the biopsy represents only a part of the lesion. Thus, in most of the cases the radiology provides the first idea about the diagnosis, & the histology confirms the final diagnosis. So good communication and cooperation is required between the clinician, radiologist & a pathologist in management of patient with bone lesions.
This study will describe how X-ray, CT and MR is useful in diagnosis and characterization of different bone tumors. [1][2][3][4]

Subjects and Methods
This was prospective study of 45 patients with bone lesions referred from orthopedic department for radiograph, CT scan and MRI study in department of Radiodiagnosis in sir sayajirao general hospital and medical college-Vadodara. This study includes clinical, radiographic, CT and MRI findings of patients with bone tumour and tumour like lesions. Institutional ethics committee has approved the study and informed written consent was taken from parents. All patients were evaluated with plain radiograph by taking at least two projections. After that CT and MRI study was performed. CT was performed by using 16 slice multi-detector spiral CT machine of General Electric. Axial as well as coronal and sagittal reconstructed CT images were acquire and evaluated. MRI was performed by using GE 1.5 TESLA Electro magnet at sahyog imaging center, medical college Vadodara. First T1W FSE and PDFS sequences with large field of view are obtained to localize area of interest using body coil. After that T1, PDFS, gradient and STIR sequences are obtained using surface coil. Post contrast T1 weighted fat saturated MR images were obtained after administration of gadolinium (0.1 mmol/kg body weight).
Bone tumours were categorized according to age group, benign or malignant, involved bone, number of lesions, pattern of bone destruction and type of matric mineralization. Data were analyzed in percentage and proportions by Microsoft excel.

Results
Total 45 patients of primary bone tumour and tumour like lesion were studied using radiography, CT and/or MRI. Out of them 21(46.6%) were female and 24(53.3%) were male. Majority of them presented with nonspecific complains of pain and swelling over local site. Most common bone involved was femur followed by tibia. Few of the lesion like osteochondroma, hemangioma and multiple myeloma showed multiple lesions.
Out of benign tumour most common benign tumour was osteochondroma (22%; n=7) followed by non-ossifying fibroma All the benign lesions had well defined margins with marrow zone of transition, whereas all the malignant lesions had illdefined margins with wide zone of transition except lesion of multiple myeloma in skull showed well defined margin with narrow zone of transition.
Six lesions (13% of cases) had pathological fracture. Out of these, two pathological fractures were missed on plain radiographs and were detected on CT and MRI scan.
Pattern of matrix mineralization was evaluated on both plain radiography and on CT scan. In 2 cases plain radiograph could not detect right matrix. Out of these two case one was of ossifying fibroma of right maxillary sinus and chondrosarcoma of metacarpal.     Radiologic diagnosis: Simple bone cyst with pathologic fracture of talus Simple bone cyst are usually painless. It show periosteal reaction only if pathologic fracture. [5] Case 5: A 25 years old female with c/o right knee pain following trauma.
Radiologic diagnosis: Fibrous cortical defect of right proximal tibia  Giant cell tumour is seen after 30 years of age however few cases are reported before 30 years. It does not show sclerotic rim. [6] Chondromyxoid fibroma and benign fibrous histiocytoma can be considered as deferential diagnosis of giant cell tumour. Chondromyxoid fibroma is seen before 30 years of age. It is also seen in epi-metaphysis however it shows peripheral sclerotic rim. [7] Benign fibrous histiocytoma is seen after 30 years. It is medullary lesion with complete or partial   peripheral sclerotic rim involving epi-metaphysis with ground glass matrix mineralization. [8][9][10] Brown's tumour of hyperparathyroidism is always a deferential diagnosis of giant cell tumour however it present with other radiographic manifestation of hyperparathyroidism and raised parathormone level. [9] Case 7: A 7 years old female child with c/o swelling over right knee.          Benign fibrous histiocytoma shows complete or partial sclerotic rim that can help in in differentiating it from giant cell tumour however it is not seen in our case. [10] Case 10: A 65 years old male with c/o swelling over left hip, h/o similar complaint in brother.

Figure 16: (A)X-ray pelvis with both hip AP view), (B,D) bilateral elbow with forearm AP and lateral view, (C,E) bilateral ankle with distal leg AP and lateral view and (F) bilateral knee AP view showing multiple sessile and pedunculated bony out growths arising from metaphases of bilateral proximal and distal femora, tibia and fibulae. Note shortening and bowing of bilateral ulna (Bayonet deformity) as well as widening of bilateral femoral,tibial and fibular metaphysis (Erlenmeyer flask deformity).
Radiological diagnosis: Diaphyseal aclasis/Multiple heteditory exostosis  Radiological differential diagnosis: Ameloblastoma, odontogenic keratocyst, aneurysmal bone cyst.
Odontogenic keratocyst are more likely to show aggressive growth pattern than other odontogenic lesions and may show multilocular appearance; this characteristics make odontogenic cyst indistigushable from ameloblastoma. [11]

Radiologic diagnosis: Multiple myeloma, Metastasis
Histopathologic diagnosis: Multiple myeloma Metastasis commonly involve vertebral pedicles rather than vertebral bodies. It rarely involve mandible. [4] Case 19: A 15 years female with c/o pain and swelling over right elbow. No history of trauma.

Histopathologic diagnosis: Ewing sarcoma
In case of ewing sarcoma a large extraosseous mass with permeative pattern of bone destruction. Fat plane is typically displaced and well defined. [2] In case of osteomyelitis soft tissue abscess simulate extraosseous tumour. Intramuscular fat planes are typically poorly defined. [2] Patient usually presents within 4 weeks. [3] In case of LCH soft tissue changes are reported however in soft tissue disease is more extensive in Ewing's sarcoma. [2] Conclusion Age of the patient and the clinical history is very crucial in drawing a reasonable diagnosis of a bone lesion. Most benign lesions are clinically asymptomatic and detected incidentally after a history of fresh trauma; while malignant lesions are having symptoms of local pain and swelling.
Plain radiography is first line imaging modality to detect and characterize a bone lesion; and to draw reasonable differential diagnosis.   CT is more sensitive than conventional radiography in detecting mineralization within the tumour matrix and pathological fracture. In areas of complex anatomy such as spine, scapula, skull and paranasal sinuses, CT was better than conventional radiography in demonstrating the lesion.
MRI is best investigation for detection of marrow infiltration, skip lesions and extension into the soft tissue.