In the name of God

1. In the name of God

2. in childrenHepatobiliary TumorsGastrointestinal Tumors in Children Radiologic Clinics of North America - Volume 49, Issue 4 (July 2011)

3. Hepatobiliary tumors are uncommon in the pediatric population, representing 5% to 6% of the abdominal tumors. Approximately one-third of hepatic lesions are benign. Metastatic liver tumors are more common thanprimary diseaseThe investigation of hepatobiliary tumors usually begins with an ultrasonographic (US) examination: readily available without ionizing radiation does not need sedation

4. The role of computed tomography (CT) is limited, in the pediatric population, because of an increase in the risk of radiation-induced cancer. Therefore, discussion of CT protocols is not the focus of this article. • Magnetic resonance (MR) imaging is a comprehensive imaging modality with multiplanar capability to assess the liver parenchyma, gallbladder, and biliary tree and is free of ionizing radiation. • MR imaging protocol consists of T1-weighted and T2-weighted fat-saturated sequences in multiple planes

5. ‘’And this one is for going into an MRI machine– alone!’’

6. Benign tumors

7. Infantile hepatic hemangioma (hemangioendothelioma): • most common benign vascular hepatic tumor in the first year of life • third most common hepatic tumor in children • may present with palpable masses, hepatomegaly, or thrombocytopenia • Multifocal lesions may present with a high-output cardiac failure • may be associated with cutaneous hemangiomas • These hemangiomas have a proliferative phase and then a phase of involution • rapid involuting congenital hemangioma (RICH) is already developed in the newborn and regresses in the first year of life.

8. MR imaging appearance of IHH is usually a low signal on T1-weighted sequences and a very high signal on T2-weighted sequences. The characteristics vary according to the presence of high-flow vessels, thrombosis, and large vascular spaces. Following intravenous gadolinium administration, they may enhance from the periphery to the center or homogenously. • US usually demonstrates hypoechoic lesions. Some lesions may be hyperechoic or with calcifications. Doppler interrogation shows abnormal vesselsand may show evidence of shunting.

9. A) Color Doppler interrogation demonstrates increased vascularity within a heterogeneous lesion in the right hepatic lobe. (B) T1-weighted image shows hypointense lesion (arrow) with high-flow vessels. (C) Fat-saturated T1-weighted image demonstrates avid enhancement of the lesion (arrow) with areas of signal void. (D) The same lesion (arrow) is hyperintense on T2-weighted sequence

11. A) Axial T1-weighted postgadolinium image showing multiple enhancing lesions of different sizes throughout the liver. (B) Coronal T2-weighted image demonstrates hyperintense lesions. (C) Color Doppler US shows one of the hypoechoic lesions with increased flow.

12. Newborn with large RICH. (A) Axial T2 fat-saturated MR image shows large hyperintense and heterogeneous mass with flow voids within the left hepatic lobe. The indicator represents measurement of the lesion. (B) Fat-saturated T1-weighted image demonstrates peripheral enhancement with no significant vascularity of the center of the lesion (arrow)

13. Most lesions resolve spontaneously and can be followed-up with MR imaging and US. • In case of cardiac failure or severe thrombocytopenia, one may consider medical therapy. • Embolization following angiography is the next step, in case medical therapy fails.

14. Mesenchymal Hamartoma • Usually seen in children up to 2 years of age. • The second most common benign hepatic tumor. • Can be cystic/multicystic or can have a more predominant stromal component with a Swiss cheese appearance. • A developmental lesion containing mesenchymal tissue with bile ducts.

15. US: usually cystic and septated and may contain a solid component. • MRI: low signal on T1-weighted sequences and of very high signal on T2-weighted sequences. • The solid component may show some degree of enhancement after intravenous gadolinium administration and may have a low T2 signal.

16. Hepatic Adenoma • Predominantly associated with certain predisposing conditions, such as GSD type 1 and Fanconi anemia, and those patients using oral contraceptives or anabolic steroids. • Single or multiple • Presence of 4 or more lesions is referred to as hepatic adenomatosis. • More commonly asymptomatic • May present with hepatomegaly and abdominal pain secondary to tumoral necrosis/hemorrhage. • In rare cases, may also rupture, causing hemoperitoneum.

17. US: the HA is of variable echogenicity and may be hypoechoic, isoechoic, or hyperechoic to the liver. • MRI:HA may present variable signal intensity characteristics on MR imaging, depending on the presence of internal hemorrhage, necrosis, or fat. T1-weighted MR sequences may show a signal intensity varying from hypointense to hyperintense. The out-of-phase T1-weighted sequences are useful to assess for the presence of a signal drop of the tumoral fatty component. On T2-weighted sequences, HA is predominantly hyperintense, but some may also be isointense to the liver • Most HAs to have a peak enhancement during the arterial phase, with a rapid washout

19. MR imaging sequences showing multiples HAs of variable sizes in a 15-years-old adolescent boy with a history of glycogen storage disease type 1. (A) Axial, breath-hold, spoiled gradient recalled (SPGR) image shows 3 well-delineated lesions that are slightly heterogeneous but with predominantly high signal intensity, involving the segments 4 and 2. (B) Axial, fat-suppressed, breath-hold, T2-weighted, fast-relaxation fast-spin echo sequence demonstrates the lesions to have heterogeneous but predominantly high signal intensity. (C) Postcontrast, axial, fat-suppressed, breath-hold, SPGR image shows significant enhancement of the adenomas.

20. Focal Nodular Hyperplasia • 2% to 6% of the hepatic tumors in childhood • usually less than 5 cm in diameter • Most cases occur in women • usually presents as a single lesion • multifocal in up to 20% of cases • surrounded by dense fibrous septa with a central prominent scar

21. US :well-delineated mass, isoechoic to the liver with a more-hyperechoic central scar • Color Doppler: increased vascularity of the fibrous septa and the central portion of the tumor, resulting in the spoke wheel pattern. • CT: The nonenhanced CT shows the lesion to be predominantly isodense to the liver. • MRI: FNH is usually isointense to the liver on both T1- and T2-weighted sequences; may also be mildly hypointense on T1-weighted or mildly hyperintense on T2-weighted sequences. • The central scar appears hyperintense on T2-weighted sequences. • Contrast-enhanced CT and MR imaging show an intense arterial enhancement that becomes isointense to the liver on the delayed sequences and delayed enhancement of the central scar

23. MR imaging showing the presence of a large FNH involving the left hepatic lobe in a 15-years-old adolescent girl. (A) Axial, breath-hold, spoiled gradient recalled (SPGR) image shows the lesion to be isointense to the hepatic parenchyma, with the central scar showing low signal intensity. (B) Axial, fat-suppressed, breath-hold, T2-weighted, fast-relaxation fast-spin echo image demonstrates the lesion to have a slightly higher signal to the liver and the central scar to have a hyperintense signal intensity. (C) Postcontrast, axial, fat-suppressed, breath-hold, 3-dimensional, SPGR image shows significant enhancement of the lesion in the arterial phase. (D) Delayed, postcontrast, axial, fat-suppressed, breath-hold, T1-weighted image shows the lesion to be almost isointense to the liver and the delayed enhancement of central scar (arrow)

25. Malignant tumors

26. Hepatoblastoma • Most common primary hepatic neoplasm of childhood and accounts for 79% of all liver tumors in children. • The typical presentation: an asymptomatic abdominal mass in a young child, usually younger than 3 years • peak incidence seen between the ages of 18 and 24 months. • Rarely, the patient may present with an acute abdomen at instances of tumor rupture. • An increased incidence has been noted in patients with Beckwith- Wiedemann syndrome, hemihypertrophy syndromes, familial adenomatous polyposis coli ,and Low–birth weight infants.

27. The tumor is usually a well-circumscribed solitary lesion with a nodular surface and usually involves the right hepatic lobe. • It can be multifocal in up to 15% of cases. • Average size at the time of diagnosis is 10 to 12 cm. • Metastases, when they occur, are usually encountered in the lungs and local lymph nodes and only rarely in the brain and bony skeleton. • 10% to 20% of cases are found to have metastatic disease at the time of diagnosis. • Elevated ɑ-fetoprotein (ɑ-FP) levels are present in as many as 90% of patients.

28. US: the lesion is usually hyperechoic, and, occasionally, intravascular tumor thrombus is seen, which can extend as far as the right atrium. CT: calcifications can be seen in about half the cases. With intravenous contrast, the lesions show slight enhancement compared with nearby liver parenchyma in the early phase of imaging, only to become isodense to hypodense with respect to liver parenchyma on delayed imaging. MRI: The appearance of hepatoblastoma on MR imaging varies with the histologic type. The epithelial type has a more homogeneous internal nature and appearance, whereas the mixed epithelial/mesenchymal type is more heterogeneous, containing fibrotic bands. The lesions show a hypointense signal relative to adjacent liver parenchyma on T1-weighted images. Occasionally, however, small hemorrhages can be seen as foci of increased signal intensity. On T2-weighted images, the tumors appear heterogeneously hyperintense in signal. Areas of fibrosis appear as bands of hypointense signal on both T1- and T2-weighted sequences.

29. Hepatoblastoma. Gray-scale (A) and color Doppler (B) US images demonstrating a large circumscribed heterogeneously slightly hyperechoic mass in the right lobe of liver with some internal flow, associated with splaying of intrahepatic vessels. (C) Enhanced CT image in portal venous phase imaging depicting the heterogeneous nature of the mass with central necrosis.

30. Multifocal hepatoblastoma MR imaging. T2-weighted (A) and postgadolinium T1-weighted SPGR (B) images show heterogeneous lesions in the liver that are slightly hyperintense on T2-weighted image and hypointense with poor enhancement on T1-weighted postgadolinium image

31. Retroperitoneal extension in a patient with small-cell undifferentiated hepatoblastoma . a CT shows a large tumour with displacement of the right branch of the portal vein (arrow) and retroperitoneal extension. b Image at a more caudal level shows involvement of the caudate lobe encasement of the main portal vein and direct extension into the pancreas

33. Hepatocellular Carcinoma • Second most common malignant liver tumor, accounting for 35% of all primary hepatic malignancies. • 2 age peaks in the pediatric population: one peak at 12 to 14 years of age and a second less-frequent peak at 2 to 4 years of age. • The typical presentation is that of a palpable abdominal mass. • Conditions predisposing to cirrhosis, such as biliary atresia, infantile cholestasis, hepatitis, glycogen storage disorders, hemochromatosis, hereditary tyrosinemia, ɑ1-antitrypsin deficiency, porphyria cutanea tarda, and Wilson disease, are associated with an increased risk for developing HCC. • Elevation of serum ɑ-FP levels is seen in up to 80% of pediatric patients with HCC.[ • Up to 50% of patients present with metastases at the time of diagnosis.

34. In the focal form, smaller lesions, generally not exceeding 3 cm in diameter, appear on US as hypoechoic circumscribed foci, whereas the larger lesions appear either hyperechoic or heterogeneous. Up to 40% of these lesions show internal calcifications with posterior shadowing. • On color Doppler interrogation, flow is seen at the periphery of the lesion but without distortion of the hepatic vasculature. • On multiphase CT, HCC appears as a mass showing precocious enhancement in the arterial phase with rapid subsequent washout on delayed imaging with capsular enhancement. Invasion of hepatic vessels can also be seen. • On MR imaging, HCC usually appears hypointense to isointense with respect to liver parenchyma on T1-weighted images and isointense to hyperintense on T2-weighted images.

35. Fibrolamellar Carcinoma This histologic variant of HCC is generally seen in adolescents and young women. US: well-circumscribed lobulated mass of variable echogenicity containing a central more-hyperechoic scar. CT: calcifications can be seen within these lesions. On multiphase imaging, the arterial phase shows the central scar, which can be hypervascular. Delayed portal venous phase images can show the lesion as isoattenuating, hypoattenuating, or hyperattenuating. MRI: hypointense on T1-weighted images and hyperintense on T2-weighted images. The internal scar appears as a central stellate region that retains contrast on portal venous phase images because of the slow washout. Because this central scar is fibrous, the signal is low on both T1- and T2-sequences, and this feature is a key to distinguishing between this entity and FNH.

36. Undifferentiated Embryonal Sarcoma • The third most common hepatic malignancy, comprising 6% of all pediatric liver tumors. • Typically presents as a rapidly growing abdominal mass, sometimes associated with pain, in an older child, usually 6 to 10 years. • Metastatic disease, when present, usually involves the lungs and bones. • A clinically important feature is that serum ɑ-FP levels remain in the normal range. • According to some investigators, UES is believed to be the malignant counterpart of mesenchymal hamartoma

37. The key imaging finding with this entity is that there is discordance between the appearance on US and on CT, with the former clearly solid with isoechoic or hyperechoic appearanceand the latter more as a well-delineated, multiseptated, fluid-appearing structurewith enhancing solid septations and a pseudocapsule. • MR: heterogeneous multiseptated cystic appearance, with hypointense signal on T1-weighted images and hyperintense signal on T2-weighted images. • A pseudocapsule with peripheral enhancement, because of compressed adjacent hepatic parenchyma, can also be seen in the early arterial phase of imaging, whereas delayed images best reveal any enhancing tumor nodules

38. Liver Metastases Metastases to the liver are most commonly from tumors arising from other intra-abdominal organs. In children, the most common tumors metastasizing to the liver are neuroblastoma and Wilms tumor. The main role of imaging is detection, characterization, and staging.

39. US : variable but is more often hypoechoic. • CT :tends to be hypodense as compared with adjacent liver parenchyma and shows variable degrees of enhancement,all depending on the primary tumor. The contrast-enhanced appearance can vary from targetlike to fairly intense and homogeneous enhancements. • MRI: more sensitive and more specific than other modalities. The MR imaging characteristics depend to a large extent on the tumor of origin. On MR imaging, most liver metastases display moderately hypointense signal on T1-weighted images and moderately hyperintense signal on T2-weighted images. • Even tiny metastases are often clearly depicted on nonenhanced fat-saturated T2-weighted images because liver metastases have extracellular matrices containing abundant free water. Occasionally, metastases with intratumoral hemorrhage or necrosis or those containing mucin may show mixed signal intensity on T1-weighted images, and those metastases with intratumoral fibrosis or necrosis may exhibit decreased signal intensity on T2-weighted images.

40. Metastases from neuroblastoma in 2 different patients. (A) CT image shows hypodense lesion in the right hepatic lobe with significant associated retroperitoneal tumor. (B) Enhanced CT demonstrates large liver with heterogeneous and hypodense parenchyma in keeping with diffuse metastatic disease from left adrenal neuroblastoma

41. Metastases from desmoplastic small round cell tumor in the left lower quadrant. US image (A) showing numerous vaguely hypoechoic mass lesions around the periphery of the liver and within the liver along the main portal vein and left branch portal vein. On CT image (B), the peripheral lesions appear extracapsular. Nodular masses in the region of the gastrohepatic ligament and along the anteromedial stomach are consistent with peritoneal implants

43. Gastrointestinal Tumors in Children

44. Although tumors arising from the spleen, pancreas, and gastrointestinal tract in the pediatric population are relatively uncommon, imaging plays an important role in diagnosis, staging, and treatment planning.

45. Pancreatoblastoma • Mean age of approximately 5 years • Male to female ratio of 2:1. • Congenital cases have been described in association with Beckwith-Wiedemann syndrome. • Patients may present with an asymptomatic abdominal mass or with nonspecific abdominal pain, vomiting, or early satiety. • ɑ-fetoprotein levels may be elevated. • Half arise from the pancreatic head; however, biliary obstruction is not a frequent presentation.

46. US and CT: pancreatoblastomas appear as well-defined, partially circumscribed, heterogeneous masses with both cystic and solid components. • MRI: most tumors are heterogeneous with low to intermediate signal intensity on T1-weighted images and high signal intensity on T2-weighted images. Heterogeneous post-contrast enhancement is a common feature. • An infiltrative pattern has also been described but is uncommon. • Small calcifications may be present. • Encasement of vascular structures, including the mesenteric vessels and the inferior vena cava, has been described, but vascular invasion is uncommon.

47. Pancreatoblastoma. A large, multilobular, mildly heterogeneous soft tissue mass is seen arising from the head and body of the pancreas. Small calcifications are seen within the mass (arrow)

48. SPEN (Solid and papillary epithelial neoplasms) • Solid-cystic papillary tumor, solid pseudopapillary tumor, papillary epithelial neoplasm, or Frantz tumor. • Most frequently reported in adolescent girls and young women with a mean age of 21 years. • Patients present with abdominal discomfort, pain, or a mass. • The course of SPENs is usually benign and tumors are limited to the pancreas in approximately 85% of the cases. • Surgery is usually curative but may require a Whipple procedure depending on location of the tumor. • Metastatic disease is rare in children.

49. On imaging, tumors are large, well-circumscribed, usually encapsulated masses, with heterogeneous architecture or mixed solid and cystic elements. Small tumors may appear completely solid. Areas of hemorrhagic necrosis, fluid–fluid levels, and blood products have been described as distinctive features. Areas of hemorrhage and blood degradation products are better depicted on MR imaging. Peripheral calcification may be present in approximately one-third of the cases Post-contrast imaging shows enhancement of the solid component or peripheral rim of enhancement of the fibrous capsule. Early peripheral enhancement and progressive centripetal filling on post-contrast dynamic MR imaging has also been described.

50.  Solid epithelial neoplasm of the pancreas in a 10-year-old girl. (A) Transverse ultrasound image shows a solid echogenic mass (M) in the head of the pancreas (P) displacing the mesenteric vessels (arrow). (B) Contrast-enhanced CT axial image shows a well-circumscribed mass (M) with heterogeneous enhancing pattern. The mass enhances less than the pancreas (P). No biliary ductal dilatation is seen.