FINDING & CONCLUSION

Irregular area of altered marrow signal intensity in diaphysis of middle one third of humerus
It appears slightly hyperintense on T2 and STIR images and hypointense on T1 w images
Heterogeneous moderately intense post contrast enhancement is noted
The lesion shows a thin irregular sclerotic margin and multiple internal septae. There is diffuse adjacent marrow edema. No fluid levels are apparent

CT images reveals irregular predominantly cortical lesion encroaching on medullary cavity. Thinning of the lateral cortex is noted with cortical breaks at multiple places. Associated circumferential periosteal reaction is noted
Intense post contrast enhancement is noted in this region. Para-osseous soft tissue component is also evident with mild post contrast enhancement extending into the adjacent muscles and intermuscular fat planes. Mild bowing of the humerus with convexity towards left side

Ewing’s Sarcoma –
Considering MRI findings-
Irregular area of altered marrow signal intensity in diaphyseal location with cortical break and associated periosteal thickening and adjacent paraosseous soft tissue.
Osteofibrous dysplasia/ossifying fibroma-
Considering CT findings –
Cortical and diaphyseal location of lesion.
Bowing of shaft of humerus.
Peripheral sclerotic margin.
Histopathological Diagnosis
Osteofibrous Dysplasia

Also called ossifying fibroma
Osteofibrous dysplasia (OFD) is a rare, benign, self-limited fibro osseous lesion that is seen almost exclusively in the diaphysis of the tibia
Other long bones are also involved but rarely
OFD is seen in patients aged < 20 years
The lesion generally involves the anterior cortex and may cause bowing of shaft of long bones
OFD typically manifests as an intracortical lytic lesion, which is generally well marginated and is often surrounded by a zone of sclerosis
Multiple lucencies may be present within the cortex, with intervening sclerotic areas
The involved cortex may be expanded and/or thickened
Periosteal reaction is rare, but when present, it is thick, solid, and chronic–appearing
OFD seldom progresses radiographically during childhood, and progression halts when the patient reaches skeletal maturity

While reporting any bone tumour/lesion consider CT also with MRI because sometimes MRI will show different findings
Considering all imaging findings we should take account of history also (as in our case pt is having h/o trivial trauma. So the soft tissue in the MRI could be secondary to pathological fracture in lesion)
Sometimes typical lesions can occur at atypical site (as in our case humerus is rare site for Osteofibrous dysplasia)

Park YK, Unni KK, McLeod RA, Pritchard DJ: Osteofibrous dysplasia: Clinicopathologic study of 80 cases. Hum Pathol 1993;24(12):1339-1347
Kahn LB: Adamantinoma, osteofibrous dysplasia and differentiated adamantinoma. Skeletal Radiol 2003;32(5):245-258
Papagelopoulos PJ, Mavrogenis AF, Galanis EC, Savvidou OD, Inwards CY, Sim FH: Clinicopathological features, diagnosis, and treatment of adamantinoma of the long bones.Orthopedics 2007;30(3):211-215
Levine SM, Lambiase RE, Perchprapa CN: Cortical lesion of the tibia: characteristic appearance at conventional radiography. Radiographics 2003;23 (1): 157 -177

October 2014