tuberculosis ( tb ) has been reported to mimic several neoplasms ; however , in our case , neoplasm is seen to mimic tb . in the initial stages of development , primary spinal neoplasms may not reveal characteristic imaging features and therefore can mimic other pathologies like spinal tb . this is of particular importance in the developing world where tb is extremely common and also in the developed world , which is witnessing a resurgence of tb with increasing number of immunocompromised patients . in september 2011 , a 22-year - old female presented with insidious onset , gradually progressive back pain and weakness in both lower limbs for 11 months . she was earlier diagnosed with tb of spine , and antitubercular chemotherapy was started . she had reduced power in both lower limbs with reduced sensations below d4 dermatome level . frontal chest radiograph revealed symmetric homogenous soft tissue density and bilateral lung field opacification in upper and middle zones [ figure 1 ] . collapse of third dorsal ( d3 ) vertebral body with resultant kyphotic deformity was seen on lateral skiagram of the dorsal spine . frontal chest radiograph ultrasound examination of bilateral upper chest revealed heterogenous mass with multiple variably sized cystic areas within [ figure 2 ] . ultrasound image of upper chest plain and contrast - enhanced computed tomography ( ct ) scans of the thorax and magnetic resonance imaging ( mri ) of the thoracic spine showed heterogenous , lytic , expansile lesion involving right transverse and spinous process of d3 vertebra with extension into the left transverse process and epidural extension with large bilateral paraspinal and mediastinal components . a diagnosis of aneurysmal bone cyst ( abc ) of posterior elements of d3 vertebra was considered on imaging . axial contrast - enhanced ct image ( a ) of the thorax at the level of d3 vertebra . axial contrast - enhanced ct image ( b ) and axial t2-weighted mr image ( c ) of the thorax at the level of arch of the aorta show multi - loculated lesion with multiple fluid - fluid levels , better seen on mri . the lesion is seen to occupy bilateral hemithoraces almost entirely at this level these imaging findings were compared with mri study performed 11 months earlier , which showed pre- and bilateral para - vertebral soft tissue lesions without loculations with involvement of vertebral body and right transverse process of d3 vertebra . epidural soft tissue was seen from first to fourth vertebral levels causing compression of the spinal cord . [ figures 4 and 5 ] axial mr images obtained 11 months earlier ( a and b ) . t1-weighted image ( a ) and t2-weighted image ( b ) show that the lesions show no loculations or septae within , hence mimicking spinal tuberculosis . axial mri ( c ) obtained later shows that the lesion has markedly increased in size with multiple loculations and fluid - fluid levels within giving the typical appearance of aneurysmal bone cyst . comparison of coronal t1-weighted mr images obtained 11 months earlier ( a ) and obtained later ( b ) a ct - guided biopsy was performed from the solid mediastinal component along with diagnostic cyst aspiration . on histologic analysis [ figure 6 ] , blood - filled lacunae separated by a spindle - cell stroma with haphazardly arranged multinucleate osteoclast - like giant cells were seen . photomicrograph ( hande 100 ) showing haphazardly arranged multinucleate osteoclast - like giant cells and spindle cell stroma aneurysmal bone cyst ( abc ) is a benign , expansile , relatively rare lesion that represents 1.4%2.3% of primary bone tumors . the cervical spine is affected in 22% of cases , the thoracic spine in 34% , the lumbar spine in 31% and the sacrum in 13% . spinal involvement is typically in the posterior elements , although extension into the vertebral body is common ( 75% of cases ) . spinal abc may extend into the adjacent vertebrae or intervertebral disk , the ribs , epidural space and the paravertebral soft tissue . abc usually occurs between the ages of 5 and 20 years with slight female predilection . most patients have pain and swelling , and vertebral lesions frequently cause signs and symptoms related to compression of the spinal cord , nerve root or both . in a study by hudson , 35% of abcs showed fluid - fluid levels at ct . visualization of fluid - fluid levels requires that the patient be motionless for approximately 10 minutes ( to allow layers to settle ) and that the imaging plane be perpendicular to the fluid levels . such scans should be viewed with a narrow window setting to identify small differences in fluid attenuation . fluid - fluid levels within abcs are indicative of hemorrhage with sedimentation and are better demonstrated with mr imaging . this case also reminds that primary spinal neoplasm should be considered a differential when symmetric opacification of lung fields on frontal chest radiographs is seen . expansile neoplasms of the spine like abc may rarely gain entry into the thoracic cavity and grow exuberantly due to negative intrathoracic pressure and relative lack of resistance . hence , such lesions in later stages of their development may mimic a malignant mediastinal mass on imaging . occasionally , vertebral hydatid cyst can also be close imaging differentials of abc of spine . our case report emphasizes that primary spinal neoplasms like abc in the initial stages can present without the characteristic imaging features and can thereby mimic spinal tb . high index of suspicion can lead to timely imaging and biopsy , strict follow - up and early detection , thereby preventing complications and difficulties in management .
a 22-year - old female presented to our services with back pain and paraparesis for 11 months . 
 she was earlier diagnosed with tuberculosis of spine , and antitubercular chemotherapy was started . 
 however her condition had worsened . 
 plain and contrast - enhanced computed tomography scans of the thorax and magnetic resonance imaging of the thoracic spine showed heterogenous , lytic , expansile lesion involving third thoracic vertebra with epidural extension and large bilateral paraspinal and mediastinal components . 
 multiple variably sized loculations with fluid - fluid levels were seen within the lesion . 
 these imaging findings suggestive of aneurysmal bone cyst of thoracic spine were compared with the findings seen 11 months earlier , which were mistaken for spinal tuberculosis . 
 histopathology confirmed the diagnosis of aneurysmal bone cyst . 
 the imaging features , diagnostic challenges and the lessons learned have been briefly discussed .