Pulmonary arteriovenous malformation mimicking a pulmonary tumour on (18)F-fluorodeoxyglucose positron-emission tomography/computed tomography.

Abstract

Pulmonary arteriovenous malformations are rare congenital abnormal connections between the pulmonary arteries and veins. The patients are usually asymptomatic [1]. Although their aetiology is unclear, it is presumed that genetic abnormalities constitute a predisposition [1, 2]. An arteriovenous malformation might cause serious complications if it remains undiagnosed and untreated [3]. We report a unique case of focal 18F-fluorodeoxyglucose (18F-FDG) uptake in a pulmonary arteriovenous malformation mimicking a mass lesion. A 74-year-old female patient with cyanosis and clubbing in her fingers and toes was referred to the Nuclear Medicine Department for positron-emission tomography (PET)/computed tomography (CT) imaging to assess a solitary pulmonary nodule with irregular margins in the right upper lobe detected on CT (Figure 1A). The CT appearance suggested a malignant lesion. On 18F-FDG PET/CT, there was increased focal uptake in the pulmonary nodule, suggesting a mass lesion, possibly malignant (Figure 1B). There is no described typical uptake pattern for arteriovenous malformations in FDG PET/CT images. 18F-FDG accumulation in a pulmonary mass suggests malignancy in most cases, although FDG accumulates in several benign conditions. Pulmonary angiography revealed afferent and efferent vessels with high contrast accumulation. Based on these findings, a pulmonary arteriovenous malformation was diagnosed. Subsequently, the patient underwent right video-assisted thoracoscopic surgery, a mini-thoracotomy, and wedge resection. The specimen confirmed the diagnosis of pulmonary arteriovenous malformation (Figure 2). Figure 1 A – CT image showing a solitary pulmonary nodule in the anterior segment of the upper pole of the right lung. B – On 18F-FDG PET/CT, increased focal uptake was seen in the pulmonary nodule, suggesting a malignancy (SUVmax 4.2 kBq/ml) Figure 2 The specimen was stained with (A) haematoxylin and eosin and (B) Elastica van Gieson, which showed large and small vessels, confirming the diagnosis of pulmonary arteriovenous malformation Pulmonary arteriovenous malformations are often diagnosed radiologically [4–6]. A chest X-ray might reveal a solitary nodule or be completely normal. Thorax CT is usually the second diagnostic tool in a patient with a suspected pulmonary arteriovenous malformation [7, 8], which causes dyspnoea and cyanosis in most cases [1, 3]. Pulmonary angiography gives the ultimate diagnostic information [4, 8]. The CT appearance of our patient's arteriovenous malformation suggested a malignant solitary mass. The moderately increased FDG uptake also caused diagnostic confusion. There is no typical uptake pattern of arteriovenous malformations in FDG PET/CT images.