|ECR 2018 / C-3084|
|Non-cystic pediatric neck masses besides nodes|
Findings and procedure details
The evaluation of a pediatric patient usually begins with gray-scale and Doppler ultrasound (US). US confirms the cystic or solid nature of the superficial masses and helps define their size and extent. Color Doppler US may demonstrate the vascularization of the mass. Deeply located masses are more difficult to access so computed tomography (CT) has an important role. CT also allows the morphologic characterization and staging and precise visualization of bone strutuctures and calcifications. MRI offers superior contrast resolution in evaluating masses but usually requires sedation in patients under 6 years old.
Imaging approach depends on age, location and composition of the mass.
The patient’s age provides important diagnostic information to the diagnosis.
Fibromatosis colli (Fig. 1)
Fibromatosis colli is a benign fusiform mass arising within the sternocleidomastoid (SCM) muscle of a neonate. There is an association with breech presentation and difficult deliveries. It presents with neck mass and torticollis with tilting of the head and rotation of the chin toward the same side. US is the imaging modality of choice and characteristic imaging findings in conjuction with clinical features usually obviate the need for additional imaging. US shows a focal mass in the muscle or diffuse enlargement that may be hypo, iso or hyperechogenic. At CT appears as isoattenuating or calcified enlargement of the sternocleidomastoid muscle. MRI may also show calcifications or signs of past intramuscular hemorrhage. There is no associated adenopathy or extramuscular extension of mass.
Infantile hemangioma (Fig. 2)
Infantile hemangioma is the most common pediatric tumor of head and neck. It appears within the first few weeks of life and is not present at birth. Rarely, infantile hemangiomas affect the airway and can be associated with obstruction presenting with biphasic stridor. Infantile hemangioma has an initial proliferative phase with rapid growth in the first year. The involuting phase occurs at 1-5 years and the involuted phase occurs at 5-7 years. At US, infantile hemangioma is a solid mass hypoechoic or heterogeneously echogenic. Color Doppler shows multiple internal vessels. At CT, proliferanting hemangioma appear as a lobulated solid mass with rapid and intense enhance after contrast and rapid washout. MRI imaging shows a isointense mass to muscle on T1 and moderately hyperintense with flow voids on T2 and robust enhancement. Involuting hemangiomas are characterized by accumulation of fibrofatty tissue.
Vascular malformations – Venous malformation (Fig. 3)
Vascular malformations are present at birth, grow slowly, commensurate with patients and do not regress spontaneously.
Venous malformations (VMs) are low-flow vascular malformations. Physical examination reveals a blue or purplish discoloration of the skin and a soft compressible mass that expands with Valsalva maneuver. VMs are usually located in the buccal region, masticator space, sublingual space, orbit, tongue and dorsal neck. Mixed lymphaticovenous malformations are common. VMs may involve superficial or deep tissues, can be transespatial, localized or diffuse. The chacarteristic image finding is the presence of phleboliths. US reveals a compressible collection of vascular channels with monophasic, low-velocity venous flow. CT and MRI demonstrates variable enhancement. Adjacent fat hypertrophy may be present.
The fascial spaces and compartments of the neck provide an approach to differential diagnosis.
Ectopic cervical thymus (Fig. 4)
Ectopic cervical thymus is usually assimptomatic and can present anywhere along the pathway of thymic descent from the angle of the madible to the superior mediastinum. US demonstrate characteristic linear echogenic septa and scattered echogenic foci. MRI imaging reveals slightly higher T1 signal than muscle and slightly less T2 signal than fat.
Ectopic thyroid can occur anywhere along the path of descent of the thyroid, most commonly occurring as lingual thyroid, posterior to the foramen cecum at the base of the tongue. US shows a mass at the base of the tongue and provides assessement for orthotopic thyroid tissue. CT demonstrates typical high attenuation.
Malignancies of the nasopharynx such as lymphoma, rhabdomyosarcoma and nasopharyngeal carcinoma, can overlap considerably with respect to their imaging appearance. Although MRI imaging appearence may sugest a particular diagnosis, its most important utility is to delineate the extent of disease.
Nasopharyngeal rhabdomyosarcoma (Fig. 5)
Rhabdomyosarcoma is the most common pediatric soft-tissue sarcoma and the second most common hed and neck malignancy. There are three histologic types: embryonal, alveolar and pleomorphic, the embryonal type occurs in 60-77% of cases and frequently envolves the head and neck. Parameningeal disease carries the worst prognosis, with extension through the epidural or meningeal space. US may show the supertficial part of a solid soft-tissue mass with heterogeneous echogenicity. CT and MRI imaging shows an inhomogeneous solid mass with strong enhancement. Intratumoral hemorrhage, bone destruction and necrosis may be present.
Nasopharyngeal carcinoma (Fig. 6)
Nasopharyngeal carcinoma (NPC) is rare in pediatric age, with children 10 to 19 years being the most commonly affected. The incidence is increased in certain geographic locations and populations, namely african american and chinese. NPC has a strong association with Epstein-Barr virus. The most common presentation is with tender cervical adenopathy. On CT and MRI, NPC appears as a large inhomogeneous mass filling the nasopharyngeal airway, with skull base erosion and intracranial extension. The tumor usually arises in the posterolateral wall of the nasopharynx in the regions of the fossa of Rosenmüller and can obstruct the lateral recess and cause assimetry of the airway. Necrotic cervical adenophaty involving the retropharyngeal and high jugular chain nodes is common.
Fat containing lesions includes teratoma, lipoma, lipoblastoma or liposarcoma.
Lipoma/Lipoblastoma/Liposarcoma (Fig. 7 and 8)
Lipomas are benign tumors of fat, usually located in the posterior triangle of neck. These tumors are commonly an incidental finding an uncommon in the first two decades of life. On imaging, lipomas are a well-defined homogeneous fatty masses.
Lipoblastoma is a benign tumor of embryonal white fat that occurs in the first 3 years of life and have two forms. The more common superficial type – benign lipoblastoma – which tens to be circunscribed and the deeper and poorly circunscribed – benign lipoblastomatosis. These tumor presents as a painless, progressively enlaring soft tissue mass and latter they mature into lipomas. The imaging appearence depends on the proportion of fat and myxoid stroma. In infants myxoid stroma may predominate and imaging findings reflect the high water content of this tissue. The myxoid stroma also enhances after contrast. Treatment of choice is wide local excision.
Liposarcomas cannot be distinguished from lipoblastomas on imaging but liposarcomas are extremely rare in children less than 10 years.
Teratoma is a common congenital neoplasm but only 5% occurs in the lateral and anterior cervical region. Teratomas appear as heterogeneous multiloculated solid and cystic masses with areas of lipid and calcifications. The lesions are usually circunscribed. US shows a heterogeneous mass with solid and cystic structures. Calcifications are more common than cartilage and bone. CT may show a hypoattenuating and heterogeneous thin-walled unilocular mass. On MRI, teratomas are hypo to isointense on T1 and hyperintense on T2.
Neurofibroma (Fig. 9)
Neurofibromas can occur in the neck in patients with neurofibromatosis (type 1). These lesions may be a single large plexiform neurofibroma or multiple small neurofibromas. MR imaging is important to assess the extension of the lesions. CT shows a central region of hypoattenuation that enhances, referred to as the target sign. MRI demonstrates a peripherally T2-weighted hyperintense mass with central hypointensity, enhancement may be heterogeneous if large. Plexiform neurofibromas are an agressive form of neurofibroma that are tortuous and have ropelike extensions along the course of the nerve with variable enhancement.
Paraganglioma (Fig. 10 and 11)
Paraganglioma is rare in the pediatric population. Some cases are sporadic but they have commonly been associated with syndromes such as von Hippel-Lindau, multiple endocrine neoplasia types IIa and IIb, neurobibromatosis type 1 and hereditary pheochromocytoma-paraganglioma syndromes. Mutations in the succinate dehydrogenase B (SDHB) are also associated with development of paragangliomas. Paraganglioma presents as a painless slow-growing mass. CT reveals a well-defined soft-tissues mass within the carotid space with homogeneous and intense enhancement. On MRI, paragangliomas exhibit hyperintense signal on T2-weighted images and iso to hypointense signl on T1-weighted images and intense contrast enhancement. The classical salt and pepper appearence represents a combination of punctate regions of hemorrhage or slow flow (salt) and flow voids (pepper).
Neuroblastoma (Fig. 12)
Neuroblastoma of head and neck frequently represents metastatis, however, primary cervical neuroblastoma occurs in 5% of cases. US reveals a solid, hypoechoic or complex mass thet may contain calcifications with or without associated enlarged lymph nodes. Neuroblastomas appear as solid, contrast-enhanced masses at CT and MRI imaging with occasional calcifications or intralesional cysts.
Fibrous connective tissue tumors (myofibroblastic tumors) constitute the largest category of nonvascular soft tissue neoplasms in the infant. This heterogeneous group includes desmoid-type fibromatosis, myofibromatosis, infantile fibrossarcoma.
Agressive fibromatosis (Fig. 13)
Agressive fibromatosis is a benign but locally agressive fibrous tumor with a tendency to infiltrate adjacent tissues. Agressive fibromatosis usually presents in the first 2 years of life, does not metastize but is known to recur after treatment. MRI image demonstrate a poorly circumscribed iso to slightly hyperintense to muscle on both T1 and T2-weighted images, with intense enhancement after contrast. The areas of low signal on the T2-weighted images are thought to indicate fibrous tissue.
Pilomatricoma (Fig. 14)
Pilomatricoma is a benign skin tumor arising from the cortex of a hair follicle. Pilomatricoma most frequently occurs in the head and neck region, usually in patients younger than 20 years. The lesion is a well-demarcated, hard and mobile superficial nodule that grows slowly. Image shows an inhomogeneous echotexture with anechoic areas representing acustic degeneration and punctate calcifications. Pilomatricomas have posterior shadowing, hypoechoic connective-tissue capsule and detectable vascularization on color Doppler.
- Nontender fusiform mass involving unilateral SCM muscle in a neonate with torticollis is almost always fibromatosis colli.
- Infantile hemangiomas have a characteristic evolution with early rapid growth and slow involution, the characteristic imaging finding is the presence of flow voids on MRI.
- Venous malfomations are low-flow malformations present at birth, the characteristic imaging finding is the presence of pheboliths.
- An older pediatric patient, male gender and Asian descent with a nasopharyngeal mass would favor carcinoma.
- Fat containing lesions includes teratoma, lipoma, lipoblastoma or liposarcoma.
- Neurofibromas and paragangliomas may be associated with certain syndromes.