A solitary extraventricular subependymal giant cell astrocytoma in the absence of tuberous sclerosis.

Subependymal giant cell astrocytomas (SEGAs) are the most common intracranial tumors in Tuberous Sclerosis Complex (TSC). Very few cases of solitary SEGA without a diagnosis of TSC have been described. Most of these previously reported solitary SEGAs were located near the caudothalamic groove or in close proximity to the lateral ventricles. Here, we describe a unique case of solitary extraventricular SEGA in a 17-year-old boy who presented with new-onset seizures in the absence of the clinical and genetic diagnosis of TSC. This extraventricular SEGA was involving white matter and cortex of the occipital lobe and was predominantly hypointense on T1 and T2-weighted images with a markedly hypointense signal on susceptibility-weighted images likely secondary to dense internal calcifications. Solitary SEGA can occur in the extraventricular location in patients without TSC and should be included in the differential diagnosis of a densely calcified supratentorial intra-axial tumor in children, especially during the second decade of life.

Imaging of Nonmalignant Adrenal Lesions in Children.

The adrenal glands in children can be affected by a variety of benign lesions. The diagnosis of adrenal lesions can be challenging, but assessment of morphologic changes in correlation with the clinical presentation can lead to an accurate diagnosis. These lesions can be classified by their cause: congenital (eg, discoid adrenal gland, horseshoe adrenal gland, and epithelial cysts), vascular and/or traumatic (eg, adrenal hemorrhage), infectious (eg, granulomatous diseases), enzyme deficiency disorders (eg, congenital adrenal hyperplasia [CAH] and Wolman disease), benign neoplasms (eg, pheochromocytomas, ganglioneuromas, adrenal adenomas, and myelolipomas), and adrenal mass mimics (eg, extralobar sequestration and extramedullary hematopoiesis). Multimodality cross-sectional imaging helps to define the origin, extent, and relationship of these lesions to adjacent structures, as well as to guide treatment management. The anatomic and functional imaging modalities used to evaluate pediatric adrenal lesions include ultrasonography, computed tomography (CT), magnetic resonance imaging, and iodine 123 metaiodobenzylguanidine scintigraphy. Identifying the imaging features of nonmalignant adrenal lesions is helpful to distinguish these lesions from malignant adrenal neoplasms. Identifying characteristic imaging findings (eg, enlarged adrenal glands, with cerebriform surface, and stippled echogenicity in CAH; a T2-hyperintense mass with avid contrast enhancement in pheochromocytoma; low CT attenuation [<10 HU] and signal intensity drop on opposed-phase chemical shift images in adenoma; and enhancing suprarenal mass supplied by a systemic feeding artery in extralobar sequestration) can aid in making the correct diagnosis. In addition, clinical features (eg, ambiguous genitalia in CAH and hypertension in pheochromocytoma) can also guide the radiologist toward the correct diagnosis. ©RSNA, 2017.

Imaging of Skeletal Disorders Caused by Fibroblast Growth Factor Receptor Gene Mutations.

Fibroblast growth factors and fibroblast growth factor receptors (FGFRs) play important roles in human axial and craniofacial skeletal development. FGFR1, FGFR2, and FGFR3 are crucial for both chondrogenesis and osteogenesis. Mutations in the genes encoding FGFRs, types 1-3, are responsible for various skeletal dysplasias and craniosynostosis syndromes. Many of these disorders are relatively common in the pediatric population, and diagnosis is often challenging. These skeletal disorders can be classified based on which FGFR is affected. Skeletal disorders caused by type 1 mutations include Pfeiffer syndrome (PS) and osteoglophonic dysplasia, and disorders caused by type 2 mutations include Crouzon syndrome (CS), Apert syndrome (AS), and PS. Disorders caused by type 3 mutations include achondroplasia, hypochondroplasia, thanatophoric dysplasia (TD), severe achondroplasia with developmental delay and acanthosis nigricans, Crouzonodermoskeletal syndrome, and Muenke syndrome. Most of these mutations are inherited in an autosomal dominant fashion and are gain-of-function-type mutations. Imaging plays a key role in the evaluation of these skeletal disorders. Knowledge of the characteristic imaging and clinical findings can help confirm the correct diagnosis and guide the appropriate molecular genetic tests. Some characteristics and clinical findings include premature fusion of cranial sutures and deviated broad thumbs and toes in PS; premature fusion of cranial sutures and syndactyly of the hands and feet in AS; craniosynostosis, ocular proptosis, and absence of hand and foot abnormalities in CS; rhizomelic limb shortening, caudal narrowing of the lumbar interpediculate distance, small and square iliac wings, and trident hands in achondroplasia; and micromelia, bowing of the femora, and platyspondyly in TD. ©RSNA, 2017.

Pediatric Fibroblastic and Myofibroblastic Tumors: A Pictorial Review.

Pediatric fibroblastic and myofibroblastic tumors are a relatively common group of soft-tissue proliferations that are associated with a wide spectrum of clinical behavior. These tumors have been divided into the following categories on the basis of their biologic behavior: benign (eg, myositis ossificans, myofibroma, fibromatosis colli), intermediate-locally aggressive (eg, lipofibromatosis, desmoid fibroma), intermediate-rarely metastasizing (eg, inflammatory myofibroblastic tumors, infantile fibrosarcoma, low-grade myofibroblastic sarcoma), and malignant (eg, fibromyxoid sarcoma, adult fibrosarcoma). Imaging has a key role in the evaluation of lesion origin, extent, and involvement with adjacent structures, and in the treatment management and postresection surveillance of these tumors. The imaging findings of these tumors are often nonspecific. However, certain imaging features, such as low or intermediate signal intensity on T2-weighted magnetic resonance images and extension along fascial planes, support the diagnosis of a fibroblastic or myofibroblastic tumor. In addition, certain tumors have characteristic imaging findings (eg, multiple subcutaneous or intramuscular lesions in infantile myofibromatosis, plaquelike growth pattern of Gardner fibroma, presence of adipose tissue in lipofibromatosis) or characteristic clinical manifestations (eg, great toe malformations in fibrodysplasia ossificans fibroma, neonatal torticollis in fibromatosis colli) that suggest the correct diagnosis. Knowledge of the syndrome associations of some of these tumors-for example, the association between familial adenomatous polyposis syndrome and both Gardner fibroma and desmoid fibromatosis, and that between nevoid basal cell carcinoma syndrome and cardiac fibroma-further facilitate a diagnosis. The recognition of key imaging findings can help guide treatment management and help avoid unnecessary intervention in cases of benign lesions such as myositis ossificans and fibromatosis colli. In this article, we describe the various types of fibroblastic and myofibroblastic tumors in children and the characteristic clinical manifestations, imaging features, and growth patterns of these neoplasms-all of which aid in the appropriate radiologic assessment and management of these lesions. (©)RSNA, 2016.

Pediatric Mediastinal Tumors and Tumor-Like Lesions.

This article reviews the imaging findings of pediatric mediastinal tumors and tumor-like lesions. The classification of the mediastinum is discussed with normal imaging appearance of the thymus in pediatric age group followed by a discussion on multiple mediastinal lesions in different compartments with emphasis on their imaging characteristics.

MRI and CT of Low-Grade Fibromyxoid Sarcoma in Children: A Report From Children's Oncology Group Study ARST0332.

OBJECTIVE: The purpose of this article is to determine the MRI and CT features of low-grade fibromyxoid sarcoma in children. MATERIALS AND METHODS: We retrospectively analyzed images of 11 pediatric patients with low-grade fibromyxoid sarcoma from a phase 3 clinical trial of nonrhabdomyosarcoma soft-tissue sarcoma (Children's Oncology Group Protocol ARST0332). MRI and CT were performed in 10 and four patients, respectively. Location, size, margin, and composition on imaging were correlated with pathologic findings. RESULTS: Tumors were located in the extremities in nine patients, and one tumor each was located in the tongue and lung. Tumors were deep in seven patients and superficial in four patients. All tumors were well defined, solitary, and nonmetastatic at presentation. Tumors were complex solid-cystic in eight patients and completely solid in three patients. On T1-weighted images, all tumors had at least some areas hypointense to muscles, and six had a split-fat sign. On STIR or T2-weighted images, eight tumors had areas hypointense to adjacent muscle, and eight tumors had fluid signal intensity. On contrast-enhanced MRI studies, eight tumors had thick enhancing internal septations, and three had peripheral nodular gyriform enhancement. When we correlated imaging to pathologic findings, areas with hypointense signal intensity on both T1- and T2-weighted images were likely related to fibrous component; areas with fluid signal intensity on T2-weighted images were likely related to myxoid component. On CT, all four tumors were hypodense to muscle, and one tumor showed punctate calcific foci. CONCLUSION: Low-grade fibromyxoid sarcoma is hypodense to muscle on CT. MRI may identify both fibrous and myxoid components of this rare pediatric soft-tissue sarcoma.

Pediatric vasculitis: recognizing multisystemic manifestations at body imaging.

Pediatric vasculitides are multisystem diseases that can be diagnostic challenges because of variable clinical manifestations. The clinical manifestation is determined by the size of the affected vessels, organs involved, extent of vascular injury, and underlying pathologic characteristics. Henoch-Schönlein purpura and Kawasaki disease are the two most common subtypes of pediatric vasculitis. Diagnosis of pediatric vasculitis can be difficult, and the outcome can be serious or fatal in the absence of timely intervention. Imaging plays a central role in establishing the diagnosis of vasculitis involving large- and medium-sized vessels, visualizing its vascular and extravascular manifestations, and monitoring the disease course and response to treatment. Although imaging cannot depict the vessel changes of small-vessel vasculitis directly, it can be used to detect tissue damage resulting from vessel inflammation. This article discusses the classification and clinical features of the major pediatric vasculitides. The imaging approach to and nonneurologic findings of major pediatric vasculitis subtypes are reviewed for the pediatric body imager.

Sonography of acute appendicitis and its mimics in children.

The diagnosis of acute right lower quadrant pain in a pediatric population is challenging. Acute appendicitis is the most common cause of an acute surgical abdomen. The common mimics of acute appendicitis are acute gastrointestinal and gynecologic diseases. This article reviews the sonographic findings of the spectrum of common acute abdominal emergencies in children with a focus on imaging clues to a specific diagnosis. This awareness can impact on diagnostic accuracy and impact patient management.

Parapharyngeal neck schwannomas with unusual vascular displacement.

This case report illustrates two unusual cases of parapharyngeal schwannomas mimicking carotid body tumors in terms of characteristic vascular displacement. Carotid body tumors classically cause splaying of internal and external carotid arteries demonstrating the Lyre sign on imaging. Also interestingly, both of these cases were seen in younger ages and include cervical sympathetic chain schwannoma and vagal schwannoma. However, these schwannomas revealed hypovascularity on imaging studies allowing differentiation from hypervascular carotid body tumors. Preoperative distinction between carotid body tumors and schwannomas is very important.

Hydranencephaly associated with cerebellar involvement and bilateral microphthalmia and colobomas.

Hydranencephaly is an encephaloclastic central nervous system disorder characterised by severe destruction of the cerebral hemispheres with preservation of posterior fossa structures. We present MRI and neurosonography features of a unique case of hydranencephaly involving cerebellum (in the form of complete liquefaction of cerebellar hemispheres) and cerebral hemispheres with associated bilateral microphthalmia and ocular colobomas. This is an exceptional case as to the best to our knowledge. In humans, such a severe involvement of cerebellum has not been reported in cases of hydranencephaly. It is essential to distinguish hydranencephaly from gross hydrocephalus, as treatment and prognosis of the two are totally different. During differentiation, it is important to remember that severe cerebellar involvement can be seen in hydranencephaly.