lung cancer is the leading cause of cancer - related mortality in both men and women throughout the world .
it is also the most commonly diagnosed cancer worldwide with most of them at an advanced stage with a poor prognosis .
a 78-year - old male smoker patient diagnosed to have non - small cell lung cancer ( nsclc ) , stage iv ( adrenal and liver metastasis ) was subjected to whole body bone scan to detect skeletal metastases , if any .
the patient had received local palliative radiotherapy 20 gy/5 # for 1 week and was on chemotherapy with gefitinib since 12 days .
increase in tracer uptake was noticed in the lower cervical vertebrae , right first rib , and medial cortical margin of the lower third of shaft of left femur [ figure 1a and b ] .
hybrid single photon emission computed tomography / computed tomography ( ct ) localized the cervical uptake to left articular process of c6 and left transverse process of c7 vertebrae with dense sclerotic changes likely degeneration due to altered weight distribution .
tc99m - methylene diphosphonate whole body bone scan in ( a ) anterior projection ( b ) posterior projection showing abnormal tracer uptake in the lower third of shaft of left femur ( arrow ) .
hybrid single photon emission computed tomography / computed tomography ( ct ) localized the ct images ( c and d ) of the lower third of the left femur showed lysis of the anteromedial cortical margin ( arrow ) ct scan of the lower third of the left femur showed lysis of the anteromedial cortical margin with no soft tissue component [ figure 1c and d ] . on the basis of bone scan and pattern of cortical bone destruction , the diagnosis of a skeletal metastasis from a bronchogenic carcinoma was suggested .
incidence of bone metastases in cancers of the breast , prostate , lung and kidney , is very high , approximately 70% of all patients .
the reported incidence of bone metastasis from nsclc is around 15%-40% , most of which involves spine , rib , and pelvis and 6% in femur .
bronchogenic carcinoma is an established entity in causing cortical bone metastases literature review also shows primaries in lung , breast , kidney , and pancreas as causes of cortical metastasis .
of particular interest is the involvement of femur with studies reporting osteolytic cortical lesions preferentially located at the femur as typical of bronchogenic carcinoma .
the reason for this special predilection for implantation in the cortical bone , particularly the femur , is still unknown .
it is speculated that the vascular network , originating in the overlying periosteum of the long bones , serves as a pathway for metastatic deposits to destruct the cortical bone .
literature review not only shows predominance of femoral involvement in bronchogenic carcinoma , but also patients with only pure cortical metastases had exclusive femoral involvement .
four distinctive patterns of bone destruction in bronchogenic carcinoma have been described . a small focal intra - cortical lesions (  cookie - bite  or  cookie - cutter  pattern ) ; large osteolytic lesions ; saucerized intra - cortical lesions with well defined periosteal reaction ; and lesions with predominant cortical destruction extending into the soft tissue as well as the medullary cavity .
the term  cookie bite metastasis  was initially coined for a small intra - cortical lesion .
although these lesions are not entirely pathognomonic , literature review shows that such lesion within the skeleton as initial diagnosis should alert the radiologist to the possibility of a primary neoplasm of the lung .
our case further illustrates how a high degree of suspicion is needed in interpreting isolated uptake in bones scan in the femur in patients with bronchogenic carcinoma .
moreover , as described in literature , the characteristic pattern of cortical destruction if found in a patient with carcinoma of unknown primary , then the search for an occult primary neoplasm should be started without delay .
 detection of skeletal metastasis in patients with lung cancer is important from management point of view . 
 we report the bone scan finding in a patient with non - small cell lung carcinoma showing isolated abnormal tracer in femur and having a characteristic appearance in computed tomography , highlighting the importance of bone scan in patients with bronchogenic carcinoma . 
INTRODUCTION
CASE REPORT
DISCUSSION