during follow - up , patients with known malignancies commonly undergo screening studies to detect recurrence or metastasis . 18f - fluorodeoxyglucose positron emission tomography ( fdg - pet ) is increasingly being used for screening , often in conjunction with computed tomography ( ct ) . overall , in the setting of an indeterminate nodule greater than 1 cm , fdg - pet has a sensitivity of 96.8% and specificity of 77.8% in the detection of malignancy . however , little is known about the accuracy of fdg - pet in detecting extrathoracic malignancies that have spread to the lungs . recently , video assisted thoracoscopic surgery ( vats ) has been performed for the resection of small pulmonary lesions . this technique is less painful and invasive , and is thus more acceptable to patients than thoracotomy . in this study the aims of the study were to determine the accuracy of fdg - pet in detecting pulmonary metastasis through the vats technique , which allows the excisional biopsy of small pulmonary nodules in patients with known malignancies . between july 2007 and april 2010 , we prospectively studied 28 patients who were in follow - up care for a previously treated malignancy . the malignancies included the colorectum ( 9 ) , breast ( 6 ) , head and neck ( 5 ) , stomach ( 3 ) , lymph ( 1 ) , ovary , uterus , liver , bladder ( table 1 ) . small pulmonary nodules had been found on chest ct and fdg - pet during routine follow - up care . diagnostic vats was then performed as part of a metastatic evaluation within a mean 20 days ( range , 2 to 90 days ) . medical records were reviewed for age , gender , primary tumor type , chest ct , and fdg - pet results , as well as histopathology of the removed nodules . chest ct results were transcribed based on the clinical report , as well as review of the images , with nodule measurement . fdg - pet imaging results with the maximum standardized uptake values ( suvmax ) were abstracted from the radiology reading at our institution . in operating room , the patient was positioned for vats . after prepping and draping , three working ports were created and the lung was visualized . an autosuture stapling device that was 45 or 60 mm long and used 4.8 mm staples was placed on an area of the lung with palpation and was fired . there were 16 men and 12 women whose median age was 56.7 years old ( range , 38 to 77 years ) . postoperative median length of chest tube drainage was 3.9 days ( range , 2 to 8 days ) . the histopathology of the nodules was metastatic adenocarcinoma in 6 ( 5 in the colorectum , 1 in the breast ) , primary adenocarcinoma in 1 ( breast ) , squamous cell in 4 ( 3 in the head and neck , 1 in the uterus ) , urothelial carcinoma in 1 , and bronchioloalveolar carcinoma in 1 . benign diagnoses included pulmonary tulberculosis in 6 , fibrosis in 5 , organizing pneumonia in 3 , and lymphoid hyperplasia in 1 ( table 2 ) . overall sensitivity of 18f - fdg - pet in the 28 patients who underwent resection was 39.2% . no association was found between malignant and benign tissue in the suvmax and tumor sizes ( table 3 ) . a receiver operating characteristics curve was constructed and a cut - off value was determined for the diagnosis of metastatic small pulmonary nodules . using the cut - off of 2.5 for the suvmax , the sensitivity and specificity for predicting metastatic small pulmonary nodules were 60.0% and 43.7% , respectively . using the cut - off of 1 mm for tumor size , the sensitivity and specificity for predicting metastatic small pulmonary nodules were 45.0% and 50.0% , respectively ( figs . 1 , 2 ) . the presumed diagnosis of small pulmonary nodules is based on several factors : the age of the patient , associated symptoms , appearance of the lesion on a radiograph , and the length of time the lesion has been present . a single pulmonary nodule is more likely to be malignant in patients with known cancer . the idea of whole body cancer surveillance is very appealing and has , for some , compelled the use of fdg - pet as a screening tool for recurrence of various malignancies . integrated fdg - pet / ct can evaluate nodules as small as 7 or 8 mm in size . a high suvmax , especially in a small pulmonary nodule , provides important information and helps guide therapy . moreover , an integrated fdg - pet / ct may provide other targets ( lymph nodes or m1 sites ) that harbor metastatic disease that require biopsy prior to resection . the optimal value of the suvmax for mediastinal and hilar lymph nodes has recently been evaluated . the usefulness of 18f - fdg - pet for differentiation of benign and malignant pulmonary lesions has been investigated in various studies [ 4 - 6 ] . the reported sensitivity and specificity of the 18f - fdg - pet ranges between 0.75 and 1.0 . suvmax were significantly increased in malignant lesions compared to benign lesions , and the value of 2.5 is accepted as the cut - off point for malignancy . suv expresses fdg uptake by the lesion normalized according to the dose administered and the subject 's body weight . in fact , having defined the many factors that can affect the uptake of labeled glucose and , therefore , the suv , it is not easy to establish fixed values that serve to distinguish between the benign and malignant nature of a small pulmonary nodule . a number of formulas designed to correct the underestimation of the suv caused by hyperglycemia , such as adjusting the value of this parameter according to the patient 's serum glucose level , have also been studied . using this method , while much has been published about the sensitivity of fdg - pet for pulmonary nodules in primary lung cancer , little information has been available on the sensitivity of pet for metastatic pulmonary lesions from extrathoracic malignancies . modern ct scanners have a far higher detection rate than ct scanners of 15 years ago . even in the case of small nodules the accurate and timely diagnosis of pulmonary nodules is essential for the proper management of patients with known malignancies . the implications of metastatic lung lesions , no matter what size , on treatment selection for patients who have received a diagnosis of a malignancy are enormous . definitive diagnosis of lung lesions can sometimes not be made because of the inaccessibility of the true lesion or the inadequacy of the sample size . bronchoscopic biopsy and percutaneous needle biopsy under ct are useful methods ; however , they are not always able to yield a definite diagnosis , since results depend on the technique and tumor size . moreover , specimens may be too small to be diagnosed , and negative biopsy results might require further examination . surgical lung biopsy is considered the final diagnostic modality to be used in patients with undiagnosed small pulmonary nodules . vats has replaced thoracotomy as the preferred surgical modality for diagnostic excisional biopsy of indeterminate pulmonary nodules because of decreased morbidity . we do use finger palpation through the port if we have difficulty identifying the lesion or the margins . we also use long roberts haemostatic clamps to feel the surface of the lung when we search for the lesion . it is generally accepted that vats biopsy reduces postoperative pain and disability , causes fewer operative scars , and is equally effective in obtaining histologic diagnosis . in patients with a history of an extrathoracic malignancy and newly diagnosed small pulmonary nodules , fdg - pet is not sensitive enough to dictate treatment . the results of this study in patients with known malignant disease reinforce the need for timely vats wedge excision of small pulmonary nodules .
backgroundthe aims of the study were to determine the accuracy of fluorodeoxyglucose positron emission tomography ( fdg - pet ) in detecting pulmonary metastasis through video - assisted thoracoscopic surgery ( vats ) , a technique that allows the excisional biopsy of small pulmonary nodules in patients with known malignancies.materials and methodsbetween october 2007 and april 2010 , 28 patients with known malignancies and small pulmonary nodules underwent vats excisional biopsies . 
 all patients were in follow - up for a previously treated malignancy . 
 the malignancies included the following : colorectum ( 9 ) , breast ( 6 ) , head and neck ( 5 ) , stomach ( 3 ) , lymph ( 1 ) , ovary ( 1 ) , uterus ( 1 ) , bladder ( 1 ) , and liver ( 1).resultsthere were 16 men and 12 women whose mean age was 56.7 years old ( range , 38 to 77 years ) . the sizes of the mean nodules removed were 11.3 mm ( range , 7 to 21 mm ) . 
 diagnoses included metastatic ( 11 ) , bronchioloalveolar carcinoma ( 1 ) , primary adenocarcinoma ( 1 ) , pulmonary tuberculosis ( 6 ) , fibrosis ( 5 ) , organizing pneumonia ( 3 ) , lymphoid hyperplasia ( 1 ) . among these lesions , 
 46.4% were malignant.conclusiontrue positive fdg - pet was 39.2% . 
 fdg - pet is not a sensitive test in the evaluation of patients with a history of an extrathoracic malignancy and newly diagnosed small pulmonary nodules . 
 vats excision allows the early diagnosis of small pulmonary nodules , with low morbidity , in patients with known malignancies .