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Fetal lung interstitial tumor: a cause of late gestation fetal hydrops
Journal of Pediatric Surgery (2011) 46, 1263–1266
www.elsevier.com/locate/jpedsurg
Independent case reports
Fetal lung interstitial tumor: a cause of late gestation fetal hydrops David A. Lazar a , Darrell L. Cass a , Megan K. Dishop b , Karolina Adam c , Olutoyin A. Olutoye d,e , Nancy A. Ayres f , Christopher I. Cassady g , Oluyinka O. Olutoye a,⁎ a
Michael E. DeBakey Department of Surgery, Texas Children's Fetal Center, Baylor College of Medicine, Houston, TX 77030, USA b Department of Pathology, The Children's Hospital, University of Colorado-Denver School of Medicine, Aurora, CO, USA c Department of Obstetrics and Gynecology, Baylor College of Medicine, Houston, TX, USA d Department of Anesthesiology, Texas Children's Hospital, Baylor College of Medicine, Houston, TX, USA e Department of Pediatrics, Texas Children's Hospital, Baylor College of Medicine, Houston, TX, USA f Division of Cardiology, Department of Pediatrics, Texas Children's Hospital. Baylor College of Medicine, Houston, TX, USA g Department of Radiology, Texas Children's Hospital, Baylor College of Medicine, Houston, TX, USA Received 3 January 2011; revised 17 February 2011; accepted 18 February 2011
Key words: Fetal lung interstitial tumor; Immature mesenchymal interstitial tumor; Fetal lung mass; Hydrops; Pleuropulmonary blastoma; Ex utero intrapartum therapy
Abstract Most fetal lung masses present by mid gestation, grow during the canalicular phase of lung development (18-26 weeks of gestation), and plateau in growth or shrink after 26 weeks of gestation. We describe the unique case of a fetal lung mass presenting at 37 weeks of gestation with hydrops and fetal heart failure. The late growth of this lesion and resultant hydrops prompted resection as part of the ex utero intrapartum treatment. Histopathology revealed a rare, recently described fetal lung interstitial tumor. This case demonstrates that a subset of fetal lung masses may continue to grow later in gestation and emphasizes the need for late gestation imaging and close follow-up in this patient cohort. © 2011 Elsevier Inc. All rights reserved.
Fetal lung anomalies are increasingly identified during obstetric ultrasound evaluation. The differential diagnosis of a fetal lung mass commonly includes congenital cystic adenomatoid malformation (CCAM; or congenital pulmonary airway malformation), bronchopulmonary sequestration, bronchial atresia, bronchogenic cyst, and congenital
⁎ Corresponding author. Tel.: +1 832 822 3135; fax: +1 832 825 3141. E-mail address: [email protected] (O.O. Olutoye). 0022-3468/$ – see front matter © 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.jpedsurg.2011.02.056
lobar emphysema [1-4]. These lesions grow during the canalicular phase of lung development (18-26 weeks of gestation), and plateau in growth, shrink, or even involute after 26 weeks [5,6]. The vast majority of fetal lung masses are benign; however, some lesions are malignant pleuropulmonary blastoma [7]. We describe the rare case of a fetal lung interstitial tumor (FLIT) presenting in the third trimester. The unique late growth of this lesion and resultant hydrops prompted resection as part of the ex utero intrapartum treatment (EXIT) (EXIT-to-resection).
1264
1. Case report A 37-year-old primigravida carrying a singleton fetus was referred to our fetal center at 36 weeks and 6 days of gestation with a large fetal lung malformation. The pregnancy had been otherwise uneventful. She had an ultrasound done at 22 weeks of gestation that was normal; however, at 36 weeks, a discrepancy between gestational age and fundal height prompted a second ultrasound. At that time, a solid, hyperechoic right-sided lung mass was identified and the patient was referred for further evaluation. Ultrafast fetal magnetic resonance imaging confirmed a 5.7 × 4.9 × 4.0-cm well-circumscribed, right-sided lesion exerting a marked mass effect with direct compression of the inferior vena cava (IVC), leftward displacement of the heart, eversion of the diaphragm into the abdomen, and compression on surrounding normal lung (Fig. 1). Fetal hydrops was present as defined by large ascites and pleural effusion, and the CCAM-volume ratio [8] was calculated to be 2.1. Fetal echocardiogram showed compression of the IVC and a large azygous vein venting venous return to the superior vena cava. The left atrium and ventricle (LV) were under filled, and there was depressed left ventricular systolic function. The LV myocardial performance index was quite elevated (0.93), indicating both diastolic and systolic LV dysfunction. Because of the presence of fetal heart failure and high likelihood of immediate respiratory insufficiency, an EXIT procedure was recommended to permit the safest delivery of the fetus. After a multidisciplinary discussion and nondirective counseling, the family elected for delivery by an EXIT procedure with resection of the thoracic mass. At 37 weeks and 1 day of gestation, an EXIT procedure was performed using the technique as previously described [9]. An endotracheal tube was placed, but ventilation was held initially to avoid high peak inspiratory pressures in the fetus' severely compressed lungs. Because of the severe compression of the IVC, a cutdown was performed to place a right internal jugular central venous catheter. Fluid was adminis-
D.A. Lazar et al. tered to optimize the fetus' volume status and avoid hypotension secondary to thoracic decompression after resection of the mass. After optimal ventricular filling was confirmed by continuous fetal echocardiography, a right posterolateral thoracotomy was performed through the fifth intercostal space. The large right lower lobe mass was partially delivered out of the chest, permitting ventilation of the compressed but otherwise normal remaining lungs with an appropriate rise in oxygen saturation. A decompressive paracentesis was performed to facilitate delivery of the fetus, and the umbilical cord was divided after 81 minutes on uteroplacental support. The child was then taken into an adjacent operating room to complete the right lower lobe resection while the mother's hysterotomy was closed. The child had an uneventful hospital course. His ventilator requirement was minimal as he was extubated on day of life (DOL) 5, and he was discharged home on DOL 21. Histopathologic examination revealed a 5.0 × 4.6 × 3.5-cm solid mass within the right lower lobe diagnosed as a FLIT, a rare, recently described lesion [10] (Fig. 2). After a multidisciplinary discussion of the case, it was decided that no adjuvant treatment was indicated. A chest x-ray and physical examination were performed for surveillance every 3 months for the first 2 years of life and once a year thereafter. At 5-year follow-up, the child had remained asymptomatic without respiratory tract infection requiring hospitalization, asthma, chest wall deformity, spinal abnormality or evidence of recurrent disease; and he had met or exceeded all developmental milestones.
2. Discussion The natural history of fetal lung masses is variable. Most of these lesions are asymptomatic in the prenatal period; however, a small percentage of lung masses will grow at a rate faster than the fetal chest. In such cases, rapid growth of the mass leads to compression of thoracic structures, fetal
Fig. 1 Sagittal (A) and coronal (B) ultrafast magnetic resonance imaging images at 36 weeks of gestation showing a fetal lung mass (M) in the setting of cardiac compression (C), pleural effusion (arrow), and ascites (A) compressing the lung (L) and everting the diaphragm into the abdomen.
Fetal lung interestrial tumor
Fig. 2 Histologic image of the FLIT showing an alveolar-like pattern of microcystic spaces and an expanded interstitium with immature-appearing mesenchymal cells.
hydrops, and, if untreated, fetal demise. Crombleholme et al [8] showed that CCAM volume growth peaks between 20 and 26 weeks of gestation, that CCAM volume growth plateaus between 26 and 28 weeks of gestation, and that no fetus had hydrops after reaching this plateau. The current literature supports the concept that by 22 weeks of gestation, most fetal lung masses have grown large enough to be identified on ultrasound [5,6,8]. Our case is unusual because no lung lesion was identified on routine ultrasound at 22 weeks, suggesting that either no lesion was present or that the lesion was too small to detect at the time. Furthermore, this lung mass seemed to grow late in gestation and led to a late onset of fetal hydrops. Review of the 22-week ultrasound images by the referring physician did not identify an earlier lesion or signs of hydrops. The images were not available to us for review. The growth of this FLIT, even in late gestation, may reflect its neoplastic pathology. Previously described as an “immature mesenchymal interstitial tumor of the lung,” a FLIT is distinct from a congenital developmental abnormality, such as a CCAM, pulmonary sequestration, or bronchial atresia [10,11]. The mass in this case contained an alveolar-like pattern of microcystic spaces lined by immature lowcuboidal alveolar-type epithelium and an expanded interstitium with immature-appearing mesenchymal cells. This mild increase in interstitial cellularity raises a differential diagnosis including low-grade pleuropulmonary blastoma (PPB)—a congenital malignancy thought to begin as a proliferation of interstitial primitive mesenchymal cells as early as 31 weeks of gestation [12]. In contrast to PPB, the mass in this case did not have the architectural features, hyperchromatic primitive spindle cell population, or immature cartilage islands typical of PPB. Chemotherapy is often recommended as adjuvant therapy for type I (cystic) PPB, particularly for ruptured or incompletely resected tumors owing to the risk of recurrence as a higher grade lesion [7,13,14]. The pathogenic relationship, if any,
1265 between FLIT and PPB remains unknown. In this case, the child was managed with close follow-up because the need for chemotherapy was uncertain. The histopathologic details of this case have been previously reported as part of a larger series by Dishop et al [10]. This report, however, expands on critical fetal, perinatal, and postoperative aspects of the case and provides a clinical reference for the prenatal presentation of FLIT. Although most fetal lung masses have a predictable pattern of growth between 20 and 26 weeks of gestation, neoplastic fetal lung masses can continue to grow late in gestation and lead to the development of hydrops during the third trimester. When rapid growth is noted in mid gestation, prenatal steroids have occasionally been used to reduce the size of the mass with some benefit [15-17]. In this case presenting so late in gestation with hydrops, steroid treatment was not administered to reduce the size of the mass nor was it offered to induce lung maturity because the EXIT procedure occurred urgently within 12 hours of evaluation. This case demonstrates that a subset of fetal lung masses may continue to grow later in gestation and emphasizes the need for late gestation imaging and close follow-up in this patient cohort. For this reason, fetuses with a lung mass are monitored at our institution for the duration of pregnancy. They are assessed with ultrasound once or twice weekly during the phase of rapid growth (depending on the size of the mass) and every other week until the mass effect resolves. Those with persistent mass effect will also undergo weekly biophysical profiles beginning at 32 weeks of gestation.
References [1] Stocker JT, Madewell JE, Drake RM. Congenital cystic adenomatoid malformation of the lung. Classification and morphologic spectrum. Hum Pathol 1977;8:155-71. [2] Stocker JT. Cystic lung disease in infants and children. Fetal Pediatr Pathol 2009;28:155-84. [3] Langston C. New concepts in the pathology of congenital lung malformations. Semin Pediatr Surg 2003;12:17-37. [4] Cass DL, Olutoye OO, Cassady CI, et al. Prenatal diagnosis and outcome of fetal lung masses. J Pediatr Surg 2011;46:292-8. [5] Kunisaki SM, Barnewolt CE, Estroff JA, et al. Large fetal congenital cystic adenomatoid malformations: growth trends and patient survival. J Pediatr Surg 2007;42:404-10. [6] Adzick NS: Management of fetal lung lesions. Clin Perinatol 2009;36: 363-76. [7] Miniati DN, Chintagumpala M, Langston C, et al. Prenatal presentation and outcome of children with pleuropulmonary blastoma. J Pediatr Surg 2006;41:66-71. [8] Crombleholme TM, Coleman B, Hedrick H, et al. Cystic adenomatoid malformation volume ratio predicts outcome in prenatally diagnosed cystic adenomatoid malformation of the lung. J Pediatr Surg 2002;37: 331-8. [9] Lazar DA, Olutoye OO, Moise KJ, et al. Ex-Utero intrapartum treatment (EXIT) procedure for giant neck masses—fetal and maternal outcomes. J Pediatr Surg (in press). [10] Dishop MK, McKay EM, Kreiger PA, et al. Fetal lung interstitial tumor (FLIT): a proposed newly recognized lung tumor of infancy to be differentiated from cystic pleuropulmonary blastoma and other
1266 developmental pulmonary lesions. Am J Surg Pathol 2010;34: 1762-72. [11] Hill DA, Dishop MK, McKay EM, et al. Immature Interstitial Mesenchymal Tumor (IIMT): a distinctive new entity of the infant lung. Presented at the Annual Meeting of the Society for Pediatric Pathology, San Diego, CA, March 24-25; 2007. [12] Hill DA, Jarzembowski JA, Priest JR, et al. Type I pleuropulmonary blastoma: pathology and biology study of 51 cases from the international pleuropulmonary blastoma registry. Am J Surg Pathol 2008;32:282-95. [13] Kirsch S, Brecht IB, Dantonello T, et al. Sixteen children with pleuropulmonary blastoma: results of the cooperative soft tissue sarcoma group. Presented at the Sarcoma Meeting, Stuttgart, Germany; 2005.
D.A. Lazar et al. [14] Priest JR, Hill DA, Williams GM, et al. Type I pleuropulmonary blastoma: a report from the International Pleuropulmonary Blastoma Registry. J Clin Oncol 2006;24:4492-8. [15] Peranteau WH, Wilson RD, Liechty KW, et al. Effect of maternal betamethasone administration on prenatal congenital cystic adenomatoid malformation growth and fetal survival. Fetal Diagn Ther 2007;22:365-71. [16] Morris LM, Lim FY, Livingston JC, et al. High-risk fetal congenital pulmonary airway malformations have a variable response to steroids. J Pediatr Surg 2009;44:60-5. [17] Curran PF, Jelin EB, Rand L, et al. Prenatal steroids for microcystic congenital cystic adenomatoid malformations. J Pediatr Surg 2010;45: 145-50.
www.elsevier.com/locate/jpedsurg
Independent case reports
Fetal lung interstitial tumor: a cause of late gestation fetal hydrops David A. Lazar a , Darrell L. Cass a , Megan K. Dishop b , Karolina Adam c , Olutoyin A. Olutoye d,e , Nancy A. Ayres f , Christopher I. Cassady g , Oluyinka O. Olutoye a,⁎ a
Michael E. DeBakey Department of Surgery, Texas Children's Fetal Center, Baylor College of Medicine, Houston, TX 77030, USA b Department of Pathology, The Children's Hospital, University of Colorado-Denver School of Medicine, Aurora, CO, USA c Department of Obstetrics and Gynecology, Baylor College of Medicine, Houston, TX, USA d Department of Anesthesiology, Texas Children's Hospital, Baylor College of Medicine, Houston, TX, USA e Department of Pediatrics, Texas Children's Hospital, Baylor College of Medicine, Houston, TX, USA f Division of Cardiology, Department of Pediatrics, Texas Children's Hospital. Baylor College of Medicine, Houston, TX, USA g Department of Radiology, Texas Children's Hospital, Baylor College of Medicine, Houston, TX, USA Received 3 January 2011; revised 17 February 2011; accepted 18 February 2011
Key words: Fetal lung interstitial tumor; Immature mesenchymal interstitial tumor; Fetal lung mass; Hydrops; Pleuropulmonary blastoma; Ex utero intrapartum therapy
Abstract Most fetal lung masses present by mid gestation, grow during the canalicular phase of lung development (18-26 weeks of gestation), and plateau in growth or shrink after 26 weeks of gestation. We describe the unique case of a fetal lung mass presenting at 37 weeks of gestation with hydrops and fetal heart failure. The late growth of this lesion and resultant hydrops prompted resection as part of the ex utero intrapartum treatment. Histopathology revealed a rare, recently described fetal lung interstitial tumor. This case demonstrates that a subset of fetal lung masses may continue to grow later in gestation and emphasizes the need for late gestation imaging and close follow-up in this patient cohort. © 2011 Elsevier Inc. All rights reserved.
Fetal lung anomalies are increasingly identified during obstetric ultrasound evaluation. The differential diagnosis of a fetal lung mass commonly includes congenital cystic adenomatoid malformation (CCAM; or congenital pulmonary airway malformation), bronchopulmonary sequestration, bronchial atresia, bronchogenic cyst, and congenital
⁎ Corresponding author. Tel.: +1 832 822 3135; fax: +1 832 825 3141. E-mail address: [email protected] (O.O. Olutoye). 0022-3468/$ – see front matter © 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.jpedsurg.2011.02.056
lobar emphysema [1-4]. These lesions grow during the canalicular phase of lung development (18-26 weeks of gestation), and plateau in growth, shrink, or even involute after 26 weeks [5,6]. The vast majority of fetal lung masses are benign; however, some lesions are malignant pleuropulmonary blastoma [7]. We describe the rare case of a fetal lung interstitial tumor (FLIT) presenting in the third trimester. The unique late growth of this lesion and resultant hydrops prompted resection as part of the ex utero intrapartum treatment (EXIT) (EXIT-to-resection).
1264
1. Case report A 37-year-old primigravida carrying a singleton fetus was referred to our fetal center at 36 weeks and 6 days of gestation with a large fetal lung malformation. The pregnancy had been otherwise uneventful. She had an ultrasound done at 22 weeks of gestation that was normal; however, at 36 weeks, a discrepancy between gestational age and fundal height prompted a second ultrasound. At that time, a solid, hyperechoic right-sided lung mass was identified and the patient was referred for further evaluation. Ultrafast fetal magnetic resonance imaging confirmed a 5.7 × 4.9 × 4.0-cm well-circumscribed, right-sided lesion exerting a marked mass effect with direct compression of the inferior vena cava (IVC), leftward displacement of the heart, eversion of the diaphragm into the abdomen, and compression on surrounding normal lung (Fig. 1). Fetal hydrops was present as defined by large ascites and pleural effusion, and the CCAM-volume ratio [8] was calculated to be 2.1. Fetal echocardiogram showed compression of the IVC and a large azygous vein venting venous return to the superior vena cava. The left atrium and ventricle (LV) were under filled, and there was depressed left ventricular systolic function. The LV myocardial performance index was quite elevated (0.93), indicating both diastolic and systolic LV dysfunction. Because of the presence of fetal heart failure and high likelihood of immediate respiratory insufficiency, an EXIT procedure was recommended to permit the safest delivery of the fetus. After a multidisciplinary discussion and nondirective counseling, the family elected for delivery by an EXIT procedure with resection of the thoracic mass. At 37 weeks and 1 day of gestation, an EXIT procedure was performed using the technique as previously described [9]. An endotracheal tube was placed, but ventilation was held initially to avoid high peak inspiratory pressures in the fetus' severely compressed lungs. Because of the severe compression of the IVC, a cutdown was performed to place a right internal jugular central venous catheter. Fluid was adminis-
D.A. Lazar et al. tered to optimize the fetus' volume status and avoid hypotension secondary to thoracic decompression after resection of the mass. After optimal ventricular filling was confirmed by continuous fetal echocardiography, a right posterolateral thoracotomy was performed through the fifth intercostal space. The large right lower lobe mass was partially delivered out of the chest, permitting ventilation of the compressed but otherwise normal remaining lungs with an appropriate rise in oxygen saturation. A decompressive paracentesis was performed to facilitate delivery of the fetus, and the umbilical cord was divided after 81 minutes on uteroplacental support. The child was then taken into an adjacent operating room to complete the right lower lobe resection while the mother's hysterotomy was closed. The child had an uneventful hospital course. His ventilator requirement was minimal as he was extubated on day of life (DOL) 5, and he was discharged home on DOL 21. Histopathologic examination revealed a 5.0 × 4.6 × 3.5-cm solid mass within the right lower lobe diagnosed as a FLIT, a rare, recently described lesion [10] (Fig. 2). After a multidisciplinary discussion of the case, it was decided that no adjuvant treatment was indicated. A chest x-ray and physical examination were performed for surveillance every 3 months for the first 2 years of life and once a year thereafter. At 5-year follow-up, the child had remained asymptomatic without respiratory tract infection requiring hospitalization, asthma, chest wall deformity, spinal abnormality or evidence of recurrent disease; and he had met or exceeded all developmental milestones.
2. Discussion The natural history of fetal lung masses is variable. Most of these lesions are asymptomatic in the prenatal period; however, a small percentage of lung masses will grow at a rate faster than the fetal chest. In such cases, rapid growth of the mass leads to compression of thoracic structures, fetal
Fig. 1 Sagittal (A) and coronal (B) ultrafast magnetic resonance imaging images at 36 weeks of gestation showing a fetal lung mass (M) in the setting of cardiac compression (C), pleural effusion (arrow), and ascites (A) compressing the lung (L) and everting the diaphragm into the abdomen.
Fetal lung interestrial tumor
Fig. 2 Histologic image of the FLIT showing an alveolar-like pattern of microcystic spaces and an expanded interstitium with immature-appearing mesenchymal cells.
hydrops, and, if untreated, fetal demise. Crombleholme et al [8] showed that CCAM volume growth peaks between 20 and 26 weeks of gestation, that CCAM volume growth plateaus between 26 and 28 weeks of gestation, and that no fetus had hydrops after reaching this plateau. The current literature supports the concept that by 22 weeks of gestation, most fetal lung masses have grown large enough to be identified on ultrasound [5,6,8]. Our case is unusual because no lung lesion was identified on routine ultrasound at 22 weeks, suggesting that either no lesion was present or that the lesion was too small to detect at the time. Furthermore, this lung mass seemed to grow late in gestation and led to a late onset of fetal hydrops. Review of the 22-week ultrasound images by the referring physician did not identify an earlier lesion or signs of hydrops. The images were not available to us for review. The growth of this FLIT, even in late gestation, may reflect its neoplastic pathology. Previously described as an “immature mesenchymal interstitial tumor of the lung,” a FLIT is distinct from a congenital developmental abnormality, such as a CCAM, pulmonary sequestration, or bronchial atresia [10,11]. The mass in this case contained an alveolar-like pattern of microcystic spaces lined by immature lowcuboidal alveolar-type epithelium and an expanded interstitium with immature-appearing mesenchymal cells. This mild increase in interstitial cellularity raises a differential diagnosis including low-grade pleuropulmonary blastoma (PPB)—a congenital malignancy thought to begin as a proliferation of interstitial primitive mesenchymal cells as early as 31 weeks of gestation [12]. In contrast to PPB, the mass in this case did not have the architectural features, hyperchromatic primitive spindle cell population, or immature cartilage islands typical of PPB. Chemotherapy is often recommended as adjuvant therapy for type I (cystic) PPB, particularly for ruptured or incompletely resected tumors owing to the risk of recurrence as a higher grade lesion [7,13,14]. The pathogenic relationship, if any,
1265 between FLIT and PPB remains unknown. In this case, the child was managed with close follow-up because the need for chemotherapy was uncertain. The histopathologic details of this case have been previously reported as part of a larger series by Dishop et al [10]. This report, however, expands on critical fetal, perinatal, and postoperative aspects of the case and provides a clinical reference for the prenatal presentation of FLIT. Although most fetal lung masses have a predictable pattern of growth between 20 and 26 weeks of gestation, neoplastic fetal lung masses can continue to grow late in gestation and lead to the development of hydrops during the third trimester. When rapid growth is noted in mid gestation, prenatal steroids have occasionally been used to reduce the size of the mass with some benefit [15-17]. In this case presenting so late in gestation with hydrops, steroid treatment was not administered to reduce the size of the mass nor was it offered to induce lung maturity because the EXIT procedure occurred urgently within 12 hours of evaluation. This case demonstrates that a subset of fetal lung masses may continue to grow later in gestation and emphasizes the need for late gestation imaging and close follow-up in this patient cohort. For this reason, fetuses with a lung mass are monitored at our institution for the duration of pregnancy. They are assessed with ultrasound once or twice weekly during the phase of rapid growth (depending on the size of the mass) and every other week until the mass effect resolves. Those with persistent mass effect will also undergo weekly biophysical profiles beginning at 32 weeks of gestation.
References [1] Stocker JT, Madewell JE, Drake RM. Congenital cystic adenomatoid malformation of the lung. Classification and morphologic spectrum. Hum Pathol 1977;8:155-71. [2] Stocker JT. Cystic lung disease in infants and children. Fetal Pediatr Pathol 2009;28:155-84. [3] Langston C. New concepts in the pathology of congenital lung malformations. Semin Pediatr Surg 2003;12:17-37. [4] Cass DL, Olutoye OO, Cassady CI, et al. Prenatal diagnosis and outcome of fetal lung masses. J Pediatr Surg 2011;46:292-8. [5] Kunisaki SM, Barnewolt CE, Estroff JA, et al. Large fetal congenital cystic adenomatoid malformations: growth trends and patient survival. J Pediatr Surg 2007;42:404-10. [6] Adzick NS: Management of fetal lung lesions. Clin Perinatol 2009;36: 363-76. [7] Miniati DN, Chintagumpala M, Langston C, et al. Prenatal presentation and outcome of children with pleuropulmonary blastoma. J Pediatr Surg 2006;41:66-71. [8] Crombleholme TM, Coleman B, Hedrick H, et al. Cystic adenomatoid malformation volume ratio predicts outcome in prenatally diagnosed cystic adenomatoid malformation of the lung. J Pediatr Surg 2002;37: 331-8. [9] Lazar DA, Olutoye OO, Moise KJ, et al. Ex-Utero intrapartum treatment (EXIT) procedure for giant neck masses—fetal and maternal outcomes. J Pediatr Surg (in press). [10] Dishop MK, McKay EM, Kreiger PA, et al. Fetal lung interstitial tumor (FLIT): a proposed newly recognized lung tumor of infancy to be differentiated from cystic pleuropulmonary blastoma and other
1266 developmental pulmonary lesions. Am J Surg Pathol 2010;34: 1762-72. [11] Hill DA, Dishop MK, McKay EM, et al. Immature Interstitial Mesenchymal Tumor (IIMT): a distinctive new entity of the infant lung. Presented at the Annual Meeting of the Society for Pediatric Pathology, San Diego, CA, March 24-25; 2007. [12] Hill DA, Jarzembowski JA, Priest JR, et al. Type I pleuropulmonary blastoma: pathology and biology study of 51 cases from the international pleuropulmonary blastoma registry. Am J Surg Pathol 2008;32:282-95. [13] Kirsch S, Brecht IB, Dantonello T, et al. Sixteen children with pleuropulmonary blastoma: results of the cooperative soft tissue sarcoma group. Presented at the Sarcoma Meeting, Stuttgart, Germany; 2005.
D.A. Lazar et al. [14] Priest JR, Hill DA, Williams GM, et al. Type I pleuropulmonary blastoma: a report from the International Pleuropulmonary Blastoma Registry. J Clin Oncol 2006;24:4492-8. [15] Peranteau WH, Wilson RD, Liechty KW, et al. Effect of maternal betamethasone administration on prenatal congenital cystic adenomatoid malformation growth and fetal survival. Fetal Diagn Ther 2007;22:365-71. [16] Morris LM, Lim FY, Livingston JC, et al. High-risk fetal congenital pulmonary airway malformations have a variable response to steroids. J Pediatr Surg 2009;44:60-5. [17] Curran PF, Jelin EB, Rand L, et al. Prenatal steroids for microcystic congenital cystic adenomatoid malformations. J Pediatr Surg 2010;45: 145-50.