technetium-99 m ( tc-99 m ) in complex with methylene - diphosphonate ( mdp ) is a commonly used substrate in radionuclide bone imaging .
bone scans utilizing this radiotracer are very sensitive and enable nuclear medicine physicians to screen for various osseous abnormalities and pathologies .
localization of the radiotracer is accomplished through the exchange of tc-99 m mdp for phosphate compounds during active bone remodeling , and aggregation is subsequently detected using a gamma camera . even though the utilization of tc-99 m mdp bone scintigraphy is useful for identifying various physiologic abnormalities , its overall specificity is limited primarily by the lack of anatomic detail .
it is therefore important to utilize the patient 's medical history , in conjunction with other forms of imaging , to aid in differentiating potential pathologies . here ,
we present a case in which tc-99 m mdp bone scintigraphy was utilized to raise concern for a serious abnormality despite relatively occult findings by conventional imaging modalities .
a 70-year - old male presented with mild left hip pain and was found to have an elevated serum alkaline phosphatase ( alk ) level of 770 units / l .
unfortunately , due to a language barrier , a complete medical history could not be obtained . in light of the patient 's elevated alk level ,
the planar whole body images [ figure 1a ] of the tc-99 m mdp bone scan demonstrated intense diffuse uptake extending from the left femoral head to the proximal shaft of the femur .
initially , we felt this type of appearance could be compatible with early paget 's disease given the markedly elevated alk , despite the absence of apparent structural deformities .
70-year - old male with mild left hip pain and elevated alkaline phosphatase diagnosed with radiogenic osteosarcoma .
( a ) the planar whole body images of the technetium-99 m methylene diphosphonate bone scan demonstrates intense diffuse uptake extending from the left femoral head to the proximal shaft of the femur ( double ended arrow ) .
( b ) the plain film of the left hip depicts three previously unreported fixation screws surrounded by osteopenic lesions ( arrow ) in the femoral neck and head . to confirm the initial diagnosis ,
the patient was sent directly for an x - ray [ figure 1b ] . however , the pattern of multifocal sclerosis ( cotton wool appearance ) that would be expected of paget 's disease was not present . instead , the radiograph demonstrated three previously unreported fixation screws , used to repair a femoral neck fracture ( later discovered to have occurred 1 year ago ) . surrounding the screws were poorly defined osteopenic , potentially lytic lesions in the femoral neck and femoral head [ figure 1b ] .
correlation of the tc-99 m mdp bone scan with the x - ray changed the initial diagnosis from suspected paget 's disease to a differential of malignancy / metastasis , reparative phase of osteonecrosis , osteomyelitis , or reactive osteolysis to the fixation screws . though simple loosening of the fixation screws could have explained the patient 's mild hip pain , the activity demonstrated by the bone scan was much too diffuse and intense to support this diagnosis . to evaluate for metastatic disease ,
a computed tomography scan of the chest , abdomen , and pelvis was ordered the following day .
evaluation of the scan of the left hip was limited due to streak artifact from the screws ; however , it was still possible to appreciate some mixed lytic / sclerotic changes in the native bone [ figure 2a and b ] .
even though these changes raised the suspicion of osseous malignancy or metastasis , they were not pathognomonic , as hardware loosening , osteopenia , and degenerative changes could have a similar appearance .
however these findings in combination with the bone scan findings , provided enough suspicion of a pathology sinister enough to refer the patient for surgical hardware revision with potential biopsy .
70-year - old male with mild left hip pain and elevated alkaline phosphatase diagnosed with radiogenic osteosarcoma .
( a and b ) computed tomography of the pelvis reveal mixed lytic / sclerotic lesions ( arrows ) within the native bone , although evaluation of the left hip was limited due to streak artifact as seen on the two axial slices in figure 1 .
surgical exploration of the left hip revealed a grossly abnormal appearance of the left proximal femur with areas of hemorrhagic bone surrounding lytic lesions .
histologic study of the biopsy [ figure 3 ] demonstrated sarcomatous , spindle shaped cells with adjacent tumor osteoid production ; represented by eosinophilic , amorphous , fibrillary deposits between individual or small aggregates of tumor cells .
70-year - old male with mild left hip pain and elevated alkaline phosphatase diagnosed with radiogenic osteosarcoma .
histologic examination of the curettage ( using hematoxylin and eosin stain , 10 ) reveals sarcomatous , spindle shaped cells ( white arrows ) with adjacent tumor osteoid production ( black arrows ) ; represented by eosinophilic , amorphous , fibrillary deposits ( white arrows ) between individual or small aggregates of tumor cells ( black arrows ) . in context , the presence of osteosarcoma was highly unlikely as there have been no case reports of primary osteosarcomas occurring in a site of a fracture that was surgically repaired 1 year prior .
additionally , the distal femur would be a far more likely site for a primary osteogenic sarcoma to occur .
however , upon further interrogation of the patient 's past medical history , it was discovered that the patient had prostate cancer 11 years ago .
given the standard of care at that time , one could surmise that he was treated with 60 - 70 gy of targeted external beam radiation to the prostate .
the dose that he received and the time frame since receiving his radiation would be compatible with radiogenic osteosarcoma as there is a latency period of about 10 years .
the repaired stress fracture 1 year prior was potentially pathologic from the malignancy , but was most likely missed due to the slightly atypical radiographic appearance on the plain film x - ray performed in the surgeon 's office .
tc-99 m mdp bone scans are very sensitive tests for detecting a wide array of abnormalities within the bone . despite its comprehensive applicability ,
it is limited in identifying specific diseases and pathologies ; often relying on the addition of other investigative modalities to reach a final diagnosis . here , a tc-99 m mdp bone scan was used to identify the presence of abnormal bone remodeling , which led to further imaging work - up and confirmatory biopsy .
osteosarcomas are particularly sensitive to tc-99 m mdp bone scans as their pathology involves active bone remodeling .
however , its presence here was unexpected due to the atypical location on the bone scan and the limited available medical history ( due to a language barrier ) . when paired with the patient 's medical history of radiation treatment and recent fracture ,
the femur would have been exposed to scatter and bremsstrahlung radiation from its proximity to the treatment field . additionally , the 10-year latency period to developing malignancy is typical for post - external beam radiation therapy induced malignancies .
the tc-99 m mdp bone scan demonstrated its value by raising the suspicion for a more sinister process in the left hip than was seen in radiographic appearance on plain film .
this case demonstrated the value of tc-99 m mdp bone scintigraphy as an initial detector of bone abnormalities .
its sensitivity prevents it from identifying specific pathologies without the aid other investigative methods as depicted in this case .
this case also underscores the importance of considering the bone scan findings in conjunction with the patient 's clinical history and anatomic imaging . by using all this information in combination
, we were able to sift through the differential and refer the patient for appropriate management .
 we present a case of a 70-year - old male who was referred for a technetium-99 m methylene - diphosphonate bone scan for mild left hip pain and an elevated alkaline phosphatase level of 770 units / l . 
 no additional information was provided and the patient 's history was limited due to a language barrier . 
 we were able to ascertain that the patient had a remote history of prostate cancer , which had been treated with radiation . 
 originally , we felt the bone scan was compatible with paget 's disease ; however , further work - up revealed the presence of osteosarcoma , which was potentially radiation - induced . 