pulmonary arteriovenous malformation ( pavm ) , first described in 1897 by churton , is characterized by abnormal communications between pulmonary veins and arteries , and is known to disturb the filtering action of pulmonary capillaries , causing thromboembolic event in systemic circulation .
most of the pavms have no symptoms , and are detected as abnormal shadow in the chest .
conclusive diagnosis is generally made by means of pulmonary arteriography or three - dimensional computed tomography ( 3d - ct ) angiography .
while hypervascular lesions can mimic pavm , we observed a rare case of a lung granuloma mimicking pavm , and performed video - assisted thoracic surgery ( vats ) .
a 76-year - old woman , who was otherwise symptom - free , was admitted to our hospital because an abnormal shadow was detected in the left lung field on her chest x - ray .
chest computed tomography ( ct ) revealed a 20  mm    14  mm nodule with well - defined margins and smooth contours in the left upper segment ( fig .
an enhanced solitary lung nodule , connected with linear structures suggestive of feeding artery and drainage vein , was revealed by contrast - enhanced 3d - ct ( fig .
arterial blood gas analysis showed hypoxemia , with arterial oxygen pressure ( pao2 ) 56  mmhg in room air .
first , the patient was placed in the right lateral decubitus position , and the left lung was deflated .
intraoperatively , elastic hard nodule was palpable in the left upper segment and bruit was not convincing .
the nodule was nontortuous in shape , covered with the visceral pleura , and neither the feeding artery nor the drainage vein was detected .
histopathological findings revealed multiple foci of coagulative necrosis surrounded by epithelioid cell granuloma containing langhans - type multinucleated giant cells , involving the medium - sized blood vessels in the pulmonary parenchyma .
the lung granuloma was difficult to be preoperatively distinguished from pavm , because hypervascular lesion such , as inflammatory changes can present as strongly enhanced nodules after injection of contrast material .
the patient had an uneventful postoperative course and was discharged 14 days after the operation .
causes of acquired or secondary pavm include chest trauma , thoracic surgery , hepatic cirrhosis , infections ( actinomycosis , schistomiasis ) , metastatic carcinoma and systemic disease . twenty eight percent of cases are considered to have no symptoms .
it was reported that when a single isolated pulmonary arteriovenous malformation is 2  cm or smaller , no symptoms appear . generally ,
when pavm is 2  cm or more , symptoms such as breathing difficulty , cyanosis , hypoxemia , finger clubbing and polycythemia occur , and the rate of occurrence of severe complications , such as rupture of the malformation , hemoptysis , cerebral infarction and cerebral abscess , is approximately 30% .
the patient in the present case was asymptomatic and had no history of chest trauma , surgery , infection or systemic disease .
abnormal vascular structures , such as pavm are not convincing in histopathological findings . coincidentally , the inflammatory granuloma of the lung looked almost identical to pavm because of the nontortuous shape with linear structures suggestive of feeding artery and drainage vein .
the resection of lung granuloma is highly successful for an isolated malformation , and mortality rate is low in this surgery .
embolization is an appropriate treatment modality in multiple pavm for which surgery is not suitable .
complications of embolization include pleuritic chest pain , pulmonary infection , air embolism , migration of coils and paradoxical embolism .
although pulmonary angiography or contrast - enhanced 3d - ct has been the standard diagnostic tool for pavm , it has limitations in detecting pavms presenting as small nodules and enhanced nodules . in our case , since the enhanced lung nodule size was 22  mm in diameter , it mimicked pavm . in this patient , it was difficult to distinguish the lung granuloma from pavm , preoperatively . though there is a report which shows lung cancer mimicking pavm , to our knowledge , this is the first report of a lung granuloma mimicking pavm .
in conclusion , clinicians should pay particular attention to enhanced nodules to rule out a variety of disorders , including neoplasm , infection , inflammatory and vascular abnormality when pavm was suspected .
for the purpose of not only diagnosis but also for safety in treatment of pavm , the surgical approach seems appropriate .
written informed consent was obtained from the patient for publication of this case report and accompanying images .
a copy of the written consent is available for review by the editor - in - chief of this journal on request .
yoshinobu ichiki : study design , data collections , data analysis , writing ; junji kawasaki : data collections ; takayuki hamatsu : data collections ; taketoshi suehiro : data collections ; makiko koike : data collections ; fumihiro tanaka : study design , data collections , data analysis ; keizo sugimachi : data collections .
 introductionwhile hypervascular lesions in the lung are known to mimic pulmonary arteriovenous malformation ( pavm ) , here we report a rare case of lung granuloma mimicking pavm , on which video - assisted thoracic surgery ( vats ) was performed.presentation of casea 76-year - old woman without any symptom was admitted to our hospital because of abnormal shadow in the left lung field on chest x - ray . 
 a 20  mm    14  mm nodule with well - defined margins and smooth contours in the left upper segment was detected in her chest computed tomography ( ct ) . 
 contrast - enhanced three - dimensional ct ( 3d - ct ) revealed an enhanced solitary lung nodule , which was connected with linear structures suggestive of feeding artery and drainage vein . 
 thus , we made a preoperative diagnosis of pavm by performing partial pulmonary resection by vats . 
 intraoperatively , elastic hard nodule was palpable in the left upper segment and bruit was not convincing . 
 histopathological findings revealed multiple foci of coagulative necrosis surrounded by epithelioid cell granuloma containing langhans - type multinucleated giant cells , involving the medium - sized blood vessels in the pulmonary parenchyma . 
 abnormal vascular structures , such as pavm were not convincing . 
 based on these findings , a diagnosis of left lung granuloma was made.discussionpreoperatively , it was difficult to distinguish the left lung granuloma from pavm , because hypervascular lesion , such as inflammatory changes can present as strongly enhanced nodules after injection of contrast material.conclusionsurgical approach seems appropriate , not only for the purpose of diagnosis , but also for the safety in treatment of a pavm . 