Case 1 -

Pulmonary Infarction Secondary to Coil Embolotherapy of Arteriovenous Malformation Presenting as a Mass Kelly J. Butnor University of Vermont/Fletcher Allen Health Care Burlington, Vermont

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Clinical History A 28 year old male presented with pleuritic chest pain, dyspnea, and low grade fever. He was a poor historian, but did state that he underwent "some lung procedure" performed by a radiologist at another institution one month prior to presentation. At presentation, a chest x-ray showed a left pleural effusion. A CT scan of the chest disclosed a large heterogeneous mass with irregular borders in the left lower lobe. The patient underwent exploratory thoracotomy with pleural fluid evacuation and wedge resection of the left lower lobe mass. Case 1 - Slide 1 Click to view with ImageScope Click to view with a Web-Based Viewer Case 1 - Figure 1 Low power view of the lung wedge resection showing diffuse hemorrhage and infarction. Case 1 - Figure 2 Organizing thrombus adjacent to area of infarction. Case 1 - Figure 3 Higher power view of organizing thrombus demonstrating refractile foreign material. Case 1 - Figure 4 Foreign material within thrombus under polarized light. Case 1 - Figure 5 EVG stain highlights abnormally dilated, closely apposed blood vessels in area of infarction. Diagnosis Pulmonary Infarction Secondary to Coil Embolotherapy of Arteriovenous Malformation Presenting as a Mass Lung Findings The lung wedge resection exhibited fibrinous pleural adhesions. Cut sections were remarkable for parenchymal hemorrhage around a nest of thin metal coils invested with white cloth-like fibers, consistent with stainless steel embolization coils. Histologic examination is notable for a pulmonary infarct accompanied by diffuse hemorrhage (Fig. 1). An adjacent organizing thrombus with refractile and polarizable material represents the remnants of the Dacron fibers with which the vascular occlusion metal coils were invested (Figs. 2-4). Although difficult to discern due to obscuring hemorrhage, careful inspection of this region also discloses abnormally dilated blood vessels in close apposition, a finding better appreciated with elastin Van Gieson (EVG) staining (Fig. 5). Discussion This case of pulmonary infarction illustrates an uncommon complication of coil embolization of pulmonary arteriovenous malformation (AVM) with an unusual radiographic appearance. Pulmonary Infarctions Presenting as Masses While characteristically wedge-shaped, pulmonary infarcts occasionally present as nodules or masses. Pulmonary infarcts lacking the typical wedge-shaped configuration are the subject of a number of case reports, ranging from infarcts that manifest as solitary pulmonary nodules to those that present as multiple pulmonary masses mimicking metastases in a patient with known malignancy. [1, 2] In a recent series detailing the presenting features of pulmonary infarctions diagnosed by surgical lung biopsy, a remarkable 65% of patients presented with solitary or multiple lung nodules/masses of undetermined nature. [3] Although the exact pathophysiologic basis for pulmonary infarcts manifesting as mass-like lesions is unclear, it is postulated that in current case, previously established collaterals around the AVM were sufficient to sustain the parenchyma distal to the infarction. Iatrogenic Causes of Pulmonary Emboli Perhaps the most familiar type of iatrogenic pulmonary embolus is bone marrow emboli seen at autopsy following cardiopulmonary resuscitation or rarely in thoracotomy specimens. Such emboli typically lodge in small-caliber arteries and are considered incidental. Clinically significant pulmonary bone marrow emboli have been reported as a complication of various orthopedic surgical procedures. [4, 5] Iatrogenic embolization of fat to the pulmonary circulation is becoming an increasingly recognized complication of body sculpting (lipoplasty) procedures, the detection of which relies on a high index of suspicion and appropriate fixation and histochemical staining techniques. [6] Bile is another endogenous substance that can embolize to the lungs. This rare and sometimes disastrous complication has been reported in a variety of hepatobiliary procedures, including percutaneous liver biopsy and ERCP. [7, 8] In addition to its accepted role in certain cosmetic surgical procedures, injectable liquid silicone (polydimethylsiloxane) is also being used by non-licensed practitioners for illicit breast augmentation and other aesthetic procedures. Rare instances of pulmonary embolization of liquid silicone, sometimes resulting in death, have been recorded. [9] On routine H&E stain, liquid silicone pulmonary emboli appear as vacuolated globules. Vascular leakage of polymethylmethacrylate (PMMA) cement, a substance used during vertebroplasties to stabilize fractures, also occasionally results in clinically significant pulmonary emboli. [10] Barium sulfate or other agents are added to most bone cements to make them radiopaque, which impart a characteristic gray-green granular appearance on histologic examination. In many cases, however, pulmonary emboli secondary to vertebroplasty are comprised of fat and/or bone marrow elements. Air and other gaseous pulmonary emboli can result from craniotomy, Caesarean section, surgeries that involve mechanical insufflation such as laparoscopy, and the insertion of intravenous catheters. [11] Diagnosis is usually based on clinical grounds and can sometimes be confirmed by imaging. Synthetic medical devices that have unintentionally embolized to the lungs include fractured intravenous catheters of various types and radioactive prostate brachytherapy seeds. While a broad range of sequelae have been reported with catheter emboli, radioactive seed emboli appear to have a remarkably low incidence of adverse clinical effects. [12, 13, 14] Transcatheter embolization therapy is a method used to treat vascular abnormalities such cerebral and pulmonary AVMs and certain hepatic malignancies. The array of embolotherapy agents includes absorbable Gelfoam, polyvinyl alcohol particles, and permanent occlusive devices. [15] Inadvertent migration to the lungs occasionally results in pulmonary infarction or death. [16, 17] Iatrogenic Causes of Pulmonary Emboli Type of Embolus Inciting Causes Histologic features Endogenous Bone marrow Fat Bile Air   CPR, orthopedic surgeries Liposuction, orthopedic surgeries Liver biopsy, ERCP Craniotomy, laproscopy, catheters   Marrow and fat elements Oil Red O-positive globules Golden-green pigment Difficult to detect Foreign Material Liquid silicone Methylmethacrylate cement Radioactive implant seeds   Cosmetic procedures Arthroplasty, vertebroplasty Prostate carcinoma brachytherapy   Vacuolated globules Green-gray granular material (rarely) ± fat and/or bone marrow Intravenous catheters Mechanical disruption Embolotherapy agents Polyvinyl alcohol particles Tris-acryl gelatin microspheres Lipidol (iodized oil) Vascular occlusion devices Detachable balloons Metallic coils (e.g. Gianturco, Nester)   Treatment of hepatic malignancies     Cerebral and pulmonary AVMs   Black-gray particles ± calcification Purple-pink homogenous particles       May see coil-associated synthetic fibers (e.g. Dacron, nylon) Pulmonary Manifestations of Hereditary Hemorrhagic Telangectasia Although no obvious mucocutaneous stigmata of hereditary hemorrhagic telangectasia (HHT), as known as Osler-Weber-Rendu, were apparent in the present case, the patient had two smaller pulmonary AVMs in additional to the large embolized lesion. It is estimated that over 80% pulmonary AVMs are congenital and of these, 80-90% are associated with HHT. [18, 19] As many as 15-35% of individuals with HHT have pulmonary AVMs, which are often multiple and typically involve the lower lobes near visceral pleural or outer third of the parenchyma. [18, 19, 20] Although two separate genetic alterations have been identified on chromosomes 9q34 and 12q, the former of which encodes endoglin, a binding membrane glycoprotein on vascular endothelial cells, the exact pathogenesis of pulmonary AVMs in HHT remains uncertain. [21] Individuals with HHT often experience hypoxia and/or dyspnea due to left-to-right shunting. Severe complications include massive hemoptysis and neurologic sequelae such as stroke. Embolotherapy of Pulmonary Arteriovenous Malformations Left untreated, pulmonary AVMs are associated with 11% mortality, therefore treatment of even asymptomatic lesions is recommended when the diameter of the feeding vessel(s) exceeds 3 mm. [20, 21] Embolotherapy using vascular occlusive devices such as detachable balloons or metallic stainless steel or platinum coils invested with synthetic fibers, such as Dacron polyester, to enhance thrombogenicity is the currently preferred method of treatment. Deployment into the AVM feeder vessel(s) is performed under radiologic guidance and post-deployment angiography is used to exclude continued perfusion. [20] Although usually safe and effective, occasional complications include fever, air emboli, and pleuritic chest pain, with pulmonary infarction occurring after as many as 5% of procedures. [20, 21, 22] References Wagner JR, Merino MJ, Pass HI, et al. Pulmonary infarcts can mimic pulmonary metastases from renal cancer. J Urol 1997;158:1688-90. Sato H, Miki M, Nakayama S, et al. Chronic solitary pulmonary nodule due to unsuspected pulmonary infarction from silent pulmonary embolism. Respirology 1996;1:303-6. Parambil JG, Savci CD, Tazelaar HD, et al. 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