Pediatric Head and Neck Masses

Is There a Mass Involving the Retina With Calcifications?

Retinoblastoma is the most common intraocular malignancy in childhood. On imaging, retinoblastoma usually appears as an intraocular mass involving the retina. Calcification is present in nearly all retinoblastomas and is considered a distinguishing feature of the disease. Although many chronic ocular processes may cause calcifications, and retinoblastoma may rarely present without calcifications, a mass involving the retina with calcifications is retinoblastoma until proved otherwise.

Retinoblastoma is not congenital but usually presents in the first few years of life. Symptoms include leukocoria (approximately half of children with leukocoria are diagnosed with retinoblastoma), squinting, and strabismus. Rarely retinoblastoma can present with extensive inflammation and be clinically mistaken for orbital cellulitis.

Retinoblastoma is caused by a defect in the RB1 tumor suppressor gene on chromosome 13q14. Mutations in both alleles are necessary for tumor development. There are hereditary and nonhereditary forms of the disease. The nonhereditary form requires spontaneous mutations in both alleles. Those with hereditary retinoblastoma already have a mutation in one allele; the other mutation occurs spontaneously. The hereditary form is more likely to present earlier and to be bilateral. Patients with the hereditary form are also predisposed to development of primary synchronous intracranial tumors, usually seen in the midline in the suprasellar region or pineal region. When retinoblastoma is present in both globes and the suprasellar location, the presentation is described as “trilateral” retinoblastoma. These intracranial tumors are histologically identical to intraocular retinoblastoma. It is for this reason that dedicated MRI of the brain, as well as the orbits, should be obtained. In addition to intracranial tumors, patients with hereditary retinoblastoma have an increased risk for development of sarcomas elsewhere. This patient population is also particularly radiosensitive, and the risk for development of sarcomas is significantly increased if radiation therapy is used for treatment.

CT shows a hyperdense retinal mass with moderate enhancement and areas of necrosis and calcification. However, CT is no longer recommended for imaging in cases of known or suspected retinoblastoma. A combination of ocular ultrasound and MRI has been proved to be adequate for tumor characterization, and this approach avoids ionizing radiation in this radiosensitive patient population.

On MRI, retinoblastoma is T1-hyperintense and T2-hypointense to the vitreous humor and demonstrates heterogenous enhancement ( Fig. 27.2 ). It is important to assess the integrity of the sclera and to evaluate the optic nerve for invasion. Evaluation of the brain should also be made with special attention to the suprasellar and pineal regions, as well as assessment for leptomeningeal disease.

The main differential diagnostic considerations for retinoblastoma are other causes of childhood leukocoria, including persistent hyperplastic primary vitreous, Coats disease, Toxocara endophthalmitis, and retinopathy of prematurity. Rarely retinal astrocytoma and medulloepithelioma may be encountered.

Is There a Mass Involving the Retina Without Calcifications?

Toxocara endophthalmitis (ocular larva migrans) is a granulomatous response to infection of the vitreous or uvea of the eye by larva of the roundworm of the Toxocara genus. The normal hosts are dogs ( T. canis ) and cats ( T. cati ), and the eggs of the parasite are excreted in animal feces. Children can become infected after ingesting eggs from contaminated items or soil. The eggs hatch in the gastrointestinal tract, and the larvae can migrate to any organ, including the eye.

The disease is usually unilateral and can result in subretinal exudate and masslike granulomas. The most common clinical presentation is visual impairment. Imaging findings are nonspecific. On CT, it may be indistinguishable from Coats disease with vitreous hyperdensity and retinal detachment. Notably, there is no calcification, which helps to distinguish it from retinoblastoma. MRI may also demonstrate a granulomatous mass that enhances after contrast administration.

Is the Mass Retrolental?

Persistent hyperplastic primary vitreous (PHPV) is the second most common cause of pediatric leukocoria. It is congenital and is usually diagnosed in the early neonatal period. The disease is almost always unilateral, and the affected eye is usually microphthalmic. Bilateral cases of PHPV may be syndromic, such as Walker-Warburg syndrome. A mimic of bilateral PHPV may be bilateral retinal detachment from trauma or condition such as Norrie disease.

Pathologically, PHPV results from failure of the embryonic primary vitreous to completely regress. The result is a residual mass of retrolental fibrovascular tissue that proliferates. It may invade the lens or bleed, resulting in increased intraocular pressures (glaucoma). Half of cases also have a persistent hyaloid canal, which contains a persistent hyaloid artery extending from the optic disc to the posterior lens. The combined shape of the retrolental mass and contiguous hyaloid canal has been likened to a martini glass. Resulting tethering of the posterior retina at the optic disc may result in varying degrees of tenting or retinal detachment. On CT the retrolental tissue is hyperdense and enhances. The residual hyaloid canal may be seen. Unlike retinoblastoma, calcifications are absent. MRI shows similar findings with an enhancing retrolental mass ( Fig. 27.3 ). Imaging findings may be complicated by the presence of intraocular hemorrhage or retinal detachment.

Does the Mass Involve the Iris?

Medulloepithelioma, a rare intraocular tumor, is a primitive neuroepithelial neoplasm. Both benign and malignant types exist. The average age at diagnosis is 5 years. Clinical findings include leukocoria, impaired vision, and pain. Most tumors originate in the ciliary body, but they can originate from the retina. CT demonstrates masses with irregular borders that can be located at the ciliary body or retina. Sometimes calcification can be seen, making this lesion difficult to distinguish from retinoblastoma when it involves the retina. On MRI the tumor is hyperintense to vitreous on T1-weighted imaging and hypointense to vitreous on T2-weighted imaging.

Is the Vitreous Abnormal Without a Discrete Mass?

Coats disease results from a congenital vascular malformation of the retina. The abnormal retinal blood vessels result in a breakdown of the blood–retina barrier. Over time this leads to the accumulation of large amounts of subretinal lipoproteins and blood products resulting in retinal detachment and vision loss. The process is commonly unilateral. Although it is congenital, it usually presents later at around 6 to 8 years of age. Symptoms include leukocoria, strabismus, glaucoma, and vision loss.

CT shows increased density in the subretinal fluid, which in some cases can be extensive enough to occupy the entire globe ( Fig. 27.4 ). Unlike retinoblastoma, there are no calcifications. After contrast, there is enhancement of the retina, but not of the subretinal space. If the subretinal fluid collection is large enough, this results in a V shape of the retina, with the apex of the V at the optic disc, where the retina is tightly attached. On MRI the subretinal fluid is hyperintense on T1-and T2-weighted imaging because of its high lipid content. If there is hemorrhage or fibrosis, this may manifest as T2 heterogeneity. As on CT, after contrast the retina enhances, but the subretinal fluid does not.

Is There Retinal Detachment?

Retinal detachment can be a complication of retinoblastoma, PHPV, Toxocara endophthalmitis, Coats disease, and medulloepithelioma. It is a nonspecific finding, but if found, a careful search should be made for associated pathology.

Is There a Mass Involving the Optic Nerve?

Optic nerve glioma is the primary consideration in an optic nerve mass or mass-like enlargement of the optic nerve in children. It can arise anywhere along the optic tracts, including the optic nerve, chiasm, and optic radiations. Histologically, optic nerve gliomas are identical to juvenile pilocytic astrocytomas. They are associated with neurofibromatosis type 1 (NF1) in half of cases, and bilateral optic nerve gliomas are diagnostic for NF1. Clinical findings include decreased vision and abnormal fundoscopic examination. On imaging the tumor most commonly presents as fusiform expansion of the optic nerve, but the mass can be eccentric. In some cases the optic nerve may be tortuous. A differential consideration for mild enlargement and enhancement may include optic neuritis, but optic nerve gliomas are typically much larger and indolent in symptom presentation.

On CT the optic nerve glioma is usually isodense to the extraocular muscles and may demonstrate variable enhancement. Calcifications are rare. On MRI the tumor is isointense or hypointense on T1-weighted imaging and hyperintense on T2-weighted imaging ( Fig. 27.5 ). Enhancement is also variable. MRI with its superior soft tissue contrast is better able to demonstrate intracranial extension. Because the only practical imaging differential of an optic nerve glioma is a nerve sheath meningioma, which is rare in the pediatric population, the imaging findings of an optic nerve glioma by MRI are essentially pathognomonic. Fortunately, optic nerve gliomas typically have an indolent course and are therefore managed conservatively.

Is the Mass Cystic and Unilocular?

Dermoid and epidermoid inclusion cysts are the most common benign extraocular orbital masses in children. They commonly occur in the upper outer orbit and may be located near to or involve cranial sutures. Clinically, they may present as facial asymmetry or become symptomatic when they are complicated by infection or cyst rupture.

Inclusion cysts are thought to originate from abnormal separation of the ectoderm from the mesoderm or aberrant in-folding of the ectoderm into the mesoderm during development and can occur anywhere throughout the head and neck. Although they are not neoplasms, they enlarge as the desquamated epithelium and/or sebum accumulates. The walls of epidermoid cysts consist only of squamous epithelium, but dermoid cysts contain dermal elements as well (hair follicles, sebaceous glands). Notably, rupture of inclusion cysts can cause an inflammatory reaction that may mimic orbital cellulitis. Imaging demonstrates well-circumscribed cystic lesions that may be adjacent to or within sutures. The adjacent bone may demonstrate remodeling, reflecting the slow growth of these lesions.

Imaging characteristics of dermoid and epidermoid cysts are similar regardless of location in the head and neck ( Fig. 27.6A–B ). These developmental cysts are commonly seen at sutures with the most common location being near the zygomaticofrontal suture (level of lateral eyebrow). Orbital location of dermoid/epidermoid cysts is not uncommon given the multiple sutures. It can be difficult to differentiate dermoid cysts from epidermoid cysts so may be referenced as "dermoid/epidermoid" cysts. Ultrasound is the most appropriate initial imaging study for palpable masses in pediatric patients, and often provides a diagnosis given history, location, and sonographic appearance. On ultrasound, dermoid/epidermoid cysts will be seen as a well-circumscribed ovoid mass within the subcutaneous tissue, and occasionally seen scalloping subjacent bone or within the suture itself. Dermoid cysts may be “solid appearing” with mixed internal echogenic material. Posterior acoustic enhancement and edge shadowing are key imaging findings to confirm the cystic nature of these pseudosolid lesions. Epidermoid cysts may be more “cystic” appearing on ultrasound and may contain internal echogenic debris.

On CT, epidermoid cysts are well circumscribed and the density slightly greater than simple fluid, reflecting the proteinaceous contents of desquamated keratinized cells. However, dermoid cysts may demonstrate lipid material secreted from the sebaceous glands, and foci of calcification may also be seen. Keratin debris within dermoid cysts may float on top of the secreted lipid giving the appearance of a fluid–fluid level. If located within bone, both dermoid and epidermoid cysts will demonstrate a well-defined lucency with a rim of sclerosis and remodeling.

On MRI, epidermoid cysts may be bright on T2-weighted imaging, but their contents are distinguished from simple fluid-containing cysts because this signal will not suppress on fluid-attenuated inversion recovery imaging and will show diffusion restriction from the keratinized cellular debris within the cyst (see Fig. 27.6C ). The lipid content of dermoid/epidermoid cysts can be isointense to mildly hyperintense on T1-weighted imaging and can show some suppression on fat-saturated sequences (suggesting dermoid).

Is There a Unilocular Cystic Lesion Near the Medial Canthus?

A dacryocystocele results from obstruction of the nasolacrimal duct. It appears as cystic dilation of the nasolacrimal duct, and may have inflammatory changes from superimposed infection causing an acute presentation (dacryocystitis). On CT and MRI a dacryocystocele appears as a thin-walled cystic lesion with fluid attenuation at the medial canthus of the eye ( Fig. 27.7 ). The lacrimal duct may be seen as a tubular structure extending distally to the valve of Hasner at its communication to the inferior turbinate. These are treated conservatively with warm compresses and massage, and antibiotics if superinfected. Other approaches, such as probing the nasolacrimal duct or rarely more aggressive surgical procedures, are reserved for difficult cases.

Is There a Unilocular Cystic Lesion That Is in Continuity With the Globe?

Coloboma results from a failure of the embryonic choroidal fissure to close. It appears as an outpouching of the globe, is usually posterior, and may involve the optic disc. However, sometimes it can be so large that it looks like an extraocular orbital cystic lesion. Bilateral colobomas are associated with CHARGE syndrome (coloboma, heart anomaly, choanal atresia, growth retardation, genital and ear anomalies).

Is the Lesion Multicystic?

Venous and lymphatic malformations represent a spectrum of slow-flow vascular malformations. These lesions are transspatial, can involve any part of the orbit and adjacent face, and typically enlarge as the patient grows.

In the orbit, superficial lesions and the superficial components of large lesions are predominantly lymphatic, while deep lesions and the deep components of large lesions are predominately venous. Although these lesions are chronic, they often present acutely with proptosis from sudden expansion caused by internal hemorrhage or secondary infection.

MRI is preferred to evaluate the depth and extent of these lesions. Venous malformations are T1-hypointense, T2-hyperintense, and enhance after contrast. Lymphatic malformations are T1-hypointense and T2-hyperintense but do not enhance, although thin septa within the lesion may show linear enhancement ( Fig. 27.8 ). Lymphatic malformations may show fluid–fluid levels from internal hemorrhage. Venous malformations may show fluid-fluid levels from extreme slow venous flow and separation of blood products. Venous malformations may also show filling defects related to clot or phleboliths.

Is the Mass Solid and Hypervascular?

Infantile hemangioma of the orbit is a benign neoplastic vascular lesion that is not congenital but develops shortly after birth, undergoes a period of rapid growth for several months (up to 1st year), and then slowly involutes over several years as it involutes into fibrous and fatty tissue. The most common orbital location is the eyelid; however, these tumors can involve the orbit and retroorbital space. Deeper masses may present with proptosis and cause complications resulting in impaired vision.

For superficial lesions with characteristic physical examination findings and an appropriate clinical history, imaging may not be needed. However, ultrasound may be requested to support a clinical diagnosis. On ultrasound, hemangiomas appear as well-defined, homogenous masses with increased vascularity. Doppler evaluation will demonstrate low resistance arterial waveforms with relatively high velocities. If the lesion is suspected to involve deeper structures, or if the diagnosis is uncertain, MRI (preferred) or CT may be helpful.

Contrast enhanced CT demonstrates a lobular homogenous soft tissue mass without calcifications. If imaged in the proliferative phase, uniform avid-enhancement is seen with contrast administration. During the involuting phase, heterogeneity of the lesion may be seen due to the fibrous and fatty components. There may be remodeling of adjacent bone, but not aggressive bony changes ( Fig. 27.9 ). On MRI an infantile hemangioma appears as a soft tissue mass, typically T1-isointense to muscle. On T2-weighted imaging, it is hyperintense to muscle and small arterial feeding vessels or flow voids are seen leading to and within the mass. Post contrast imaging during the proliferative phase demonstrates an avid enhancement beginning in the arterial phase with enhancement similar in signal to the aorta. During the involuting phase, heterogeneity can be seen. Asymptomatic lesions can be observed, and treatment with propranolol or surgery may be recommended for symptomatic lesions or lesions which could cause visual symptoms with lesion growth.

Does the Mass Appear Aggressive, Eroding Adjacent Bone?

Is the mass in the Bony Orbit?

Langerhans cell histiocytosis (LCH) is a multisystem disease that has many clinical presentations. With orbital disease, patients most commonly present with proptosis. Additional symptoms include ptosis and palpebral or periorbital erythema. In the setting of orbital involvement, LCH is most commonly found in the lateral aspect of the frontal bone but can be found in other bones and extend into nearby soft tissues. Because they are locally aggressive, they need to be distinguished from other aggressive, potentially malignant lesions.

CT demonstrates a relatively homogenous soft tissue mass centered in and eroding the involved bone ( Fig. 27.10 ) with well defined margins. The mass enhances homogeneously after contrast. On MRI, these lesions are T1-intermediate and T2-hyperintense. Like CT, on MRI they enhance after contrast.

The discovery of Langerhans cell histiocytosis of the orbit should initiate an evaluation for systemic disease. The treatment depends on the disease extent. Single lesions may heal spontaneously and are frequently observed after diagnostic biopsy, but multifocal disease may require a more aggressive approach with steroids and chemotherapy.

Is the mass Centered in the Bone of the Lateral Orbital wall with an Aggressive Periosteal Reaction?

Neuroblastoma is the most common pediatric malignancy to metastasize to the orbit. The metastases typically involve the bones of the lateral orbital wall and orbital roof. Clinical findings usually consist of proptosis and periorbital ecchymosis.

CT demonstrates a soft tissue mass involving the bone with a permeative or erosive appearance ( Fig. 27.11 ). There is typically an aggressive periosteal reaction with a “sunburst” pattern. The soft tissue component is typically hyperdense to muscle and may contain small calcifications and areas of cystic necrosis. The soft tissue component may extend into the lateral extraconal space, but only rarely does it involve the preseptal space. On MRI the soft tissue component is T1-hypointense to muscle, T2-hyperintense to muscle, and demonstrates heterogenous enhancement.

Is there an Expansile, Ground-Glass Appearance to the Bony Orbit?

Fibrous dysplasia is a developmental abnormality of the bones consisting of immature fibroosseous tissue that slowly grows over time. Most cases involve only one bone, but the disease can be polyostotic. Notably, polyostotic fibrous dysplasia is associated with McCune-Albright syndrome. When it involves the orbit, patients may present with facial deformity or visual impairment.

Classically, radiographs usually show a ground-glass matrix within a defined lesion centered in the medullary space with expansion and remodeling of the involved bone. There may be scattered areas of sclerosis. Similar to radiographs but with better anatomic detail, CT demonstrates a predominantly ground-glass lesion with scattered areas of sclerosis ( Fig. 27.12 ). MRI shows low to intermediate signal on T1 and variable signal on T2. Nuclear medicine bone scans show increased activity on all phases, and F-18 fluorodeoxyglucose-positron emission tomography/CT shows intense hypermetabolic activity.

Is the Mass Continuous With the Brain Through a Cranial Defect?

An encephalocele in the nasal region usually results from herniation of brain tissue through either a persistent fonticulus frontalis or prenasal space. Nasofrontal cephaloceles protrude through a persistent fonticulus frontalis, while nasoethmoidal cephaloceles protrude through a persistent prenasal space. Clinically, patients may present with a mass over the nasal bridge that enlarges when crying and hypertelorism. The mass may or may not be covered by skin. For the diagnosis of an encephalocele to be made, the extracranial mass and associated cerebral spinal fluid must be continuous with the intracranial brain and subarachnoid space, respectively. On MRI, herniated brain tissue present in the encephalocele should be similar in intensity with contiguous intracranial brain tissue however may be T2-hyperintense because of gliosis. Cerebrospinal fluid in an encephalocele will be T1-hypointense and T2-hyperintense. Like normal brain tissue, brain tissue in an encephalocele does not typically enhance. The cranial defect through which the encephalocele protrudes will often be wide with erosion of the anterior aspect of the crista galli ( Fig. 27.13 ). Imaging is performed to evaluate the encephalocele, for potential presurgical planning, and to look for associated anomalies, including intracranial cysts, callosal agenesis, interhemispheric lipomas, and schizencephaly.

Is the Mass Discontinuous With Brain Tissue?

A nasal glial heterotopion or nasal cerebral heterotopion is brain tissue that herniates within the dural diverticulum in the prenasal space, then subsequently loses continuity with the intracranial brain. It is not a neoplasm, and so the term nasal glioma is not preferred. The sequestered brain tissue typically consists of dysplastic neuroglia and fibrovascular tissue. These lesions may be midline or just off midline.

Nasal glial heterotopia are classified as intranasal or extranasal. Intranasal heterotopia are found on the lateral wall or nasal septum of the nasal cavity and may present with nasal obstruction. Extranasal glial heterotopia are found on the bridge of the nose. Unlike an encephalocele, heterotopia typically will not enlarge with crying, but hypertelorism may be present. On MRI, they are typically isointense to brain matter on T1-weighted imaging and T2-weighted imaging ( Fig. 27.14 ). A fibrous stalk may be seen attaching the nasal glioma to the brain. Nasal heterotopia do not enhance, but with intranasal heterotopia there may be enhancement of the adjacent compressed nasal mucosa.

Is There a Persistent Sinus Tract or Inclusion Cyst?

A persistent sinus tract may be found anywhere along the path between the foramen cecum at the anterior skull base to the bridge of the nose. It forms when the dural diverticulum, which protrudes through the embryonic prenasal space, fails to completely regress. If the tract is continuous from the skin to the meninges, there may be a history of recurrent meningitis from bacteria normally found on the skin surface. Sometimes a small pit with hairs or sebaceous secretions is visible on the bridge of the nose.

In addition to a persistent sinus tract, the dural diverticulum can fail to completely separate from its point of contact with the skin and, as it regresses back to the cranial vault, can contain a small amount of ectoderm, forming a dermoid or epidermoid inclusion cyst. Nasal dermoid and epidermoid cysts have similar imaging characteristics as these lesions found elsewhere in the body.

Is the Mass Hypervascular?

Infantile hemangiomas can occur anywhere in the head and neck, but infantile hemangiomas of the nasal bridge are significant because they must be distinguished from other nasal bridge masses, including encephalocele, nasal glioma, and nasal dermoid/epidermoid. These lesions can appear similar on clinical examination, so imaging is crucial to assist with diagnosis and to exclude intracranial involvement of nasal bridge masses. Infantile hemangiomas are not congenital but arise shortly after birth, undergo rapid growth for about a year, and then slowly involute. Imaging characteristics are further characterized later in this chapter.