|ECR 2018 / C-3156|
|Imaging neck masses in children - a pictorial review with focus on ultrasound|
Findings and procedure details
US is the method of choice when approaching pediatric neck masses and therefore this presentation will focus on the US examination and when necessary will make reference to MR or CT.
US examination technique
The patient is examined in a supine position with a pillow or the hand of the mother placed under the shoulders of the child in order to obtain proper head extension.
Since the targeted lesions are mainly superficial, the examination is routinely performed with a linear transducer (7-14 MHz) to ensure a detailed visualization and characterization of the neck structures and encountered lesions.
When large lesions are encountered a curvilinear transducer may also be used to appreciate their margins, exact location and relationship with neighboring structures. Yet in these situations further imaging is required.
US Anatomy of the neck
Some of the neck lesions are space specific, while others may arise in various areas of the neck. Still, a solid knowledge and understanding of the neck anatomy is mandatory for the evaluation of neck masses, both for diagnosis as well as for appreciating extension and accurate localization. (Fig. 1)
Neck masses classifications
Due to their heterogeneity neck masses may be subdivided in various ways: upon their cystic or solid nature, age at presentation, etiology or anatomic location. None of these classifications is better than the other and actually all of the criteria are to be considered when making a diagnosis. (Table I)
1. Thyroglossal duct cyst
Thyroglossal duct cysts are very common among pediatric patients. They arise on the anterior midline of the neck and may be found anywhere along the thyreoglossal duct which extends from the base of the tongue to the foramen caecum of the thyroid.
US findings: they appear as round/oval fluid-filled lesions. Depending on the content they may be anechoic, hypoechoic or with internal echoes if hemorrhage or infection occurred. (Fig. 2, 3, 4)
2. Dermoid cyst is a broad term which usually includes epidermoid cysts, dermoid cysts and teratomas. These are usually a rare cause for swelling of the neck, but must be taken into consideration in the differential diagnosis. They are located close to the hyoid bone, close to the midline, sometimes in the mouth floor.
US findings: well-circumscribed oval shape lesion, variable internal echogenicity, depending on the fat content, with acoustic shadowing and sometimes calcifications.
3. Brachial cleft cysts represent embryological developmental alterations of one of the four branchial arches, their incomplete obliteration causing the formation of cysts (most cases), sinuses or fistulas.
Most of these lesions are remnants of the second branchial cleft, often found in the submandibular area, but also in the anterior triangle of the neck, close to the anterior margin of the sternocleidomastoid muscle. Cysts encountered at the level of the thyroid gland represent remnants of the third or fourth brachial arch.
US aspect: hypoechoic, fluid filled cystic mass, with internal echoes (cholesterol crystals), usually homogeneous, causing acoustic shadowing. Yet, sometimes they may appear inhomogeneous if septations develop or if complications occur (infection, hemorrhage). Fig. 6
4. Ranulas represents a fluid-filled lesion, caused by the obstruction of the sublingual salivary gland.
US findings: submental or submandibular anechoic mass in relationship with the sublingual gland. (Fig. 7)
1. Inflammatory lymph nodes
Reactive inflammatory lymph nodes represent a response to the infection or inflammation of the neighboring structures (salivary glands, tonsils, teeth, ear etc)
US findings: normally lymph nodes are oval, hypoechoic with an echoic center. When infection or inflammation occurs they become slightly enlarged, more hypoechoic than normal and have a broader echogenic center.(Fig. 8)
Lymphadenitis is an infection of the lymph-node itself,
either bacterial or viral (frequently Staphylococcus aureus or B-hemolytic Streptococcus).
The lymphnodes are swollen, painful at palpation and the suprajacent skin becomes warm and red.
US findings: lymph nodes become enlarged, with small hypoechoic areas (liquefaction) and inflammation of the surrounding fat. (Fig. 9, 10)
3. Lymph node abscess
Abscess formation within a lymph node is difficult to diagnose only by clinical evaluation and therefore imaging is necessary.
US findings: hypoechoic central areas of fluid surrounded by a wall or collections with floating echo-reflections are suggestive for abscess formation.
Even though these features are rather specific, according to literature US is not entirely reliable in imaging abscess and sometimes further imaging is required in order to accurately determine the size of the abscess and its effect on the other neck structures (MR, CT).
4. Lymphoma often presents as a painless, large lymphadenopathy, cervical nodes being most commonly associated with Hodgkin lymphoma.
On ultrasound the affected nodes are round, homogeneously hypoechoic and the normal echogenic hilum is absent.
US findings: large, numerous, well-circumscribed, rounded nodes with reduced echogenicity, altered vascularity and an absent hilum. These findings are not specific for lymphoma and therefore biopsy and histology are mandatory. (Fig. 12, 13, 14)
Further imaging (MR, PET-CT) are required to determine extension of the disease.
Pathology of the salivary glands includes mainly infections (viral or bacterial), parotid hemangiomas, autoimmune and granulomatous diseases, lithiasis, tumors (rare)
5. Parotitis - can be either bacterial or viral, acute or chronic, uni- or bilateral.
US findings: the gland becomes larger, inhomogeneous (with small hypoechoic areas inside), increased vascularity and reactive lymphnodes inside. (Fig. 15, 16)
Thyroid lesions among pediatric patients include congenital lesions (such as aplasia/hypoplasia or ectopic thyroid), inflammatory (thyroiditis) and neoplastic lesions. (Fig. 17, 18, 19, 20, 21)
6. Thyroiditis (Hashimoto and Basedow-Graves disease)
In both Hashimoto's thyroiditis and Basedow-Graves disease may present with an enlarged, palpable thyroid gland.
Hashimoto's thyroiditis is an autoimmune disease associated mainly with hypothyroidism.
US findings: include an enlarged gland, with a very inhomogeneous, nodular structure, sometimes with increased vascularity (but vascularity may be normal) (Fig. 22, 23). In the course of the disease the gland gets smaller in size, develops internal echoic, fibrotic septations.
In Basedow-Graves disease the thyroid gland is even more enlarged and the vascularity is extremely increased (Fig. 24). The Color Doppler appearance in Basedow has been described as a red-blue inferno. (Fig. 25)
7. Thyroid cysts and nodules - are very common and can be either single or multiple, purely cystic or solid and sometimes complex.
On ultrasound thyroid cysts can be anechoic, sometimes with bright internal spots (colloid cysts) or hypoechoic with acoustic shadowing.
Thyroid nodules are usually isoechoic compared to the normal gland.
When evaluating the thyroid nodules one must be aware of signs of malignancy: nodules that increase in size, hypoechogenicity, calcifications, complex lesions (cysts with mural nodules), altered vascularity, enlarged lymphnodes.
Papillary carcinoma is the most frequent thyroid malignancy and has usually a favorable prognosis. (Fig. 26, 27)
The neck is an area with multiple muscles which may cause neck swelling. Sometimes it is a pathology of the muscle itself (inflammatory, autoimmune, traumatic, tumoral) while sometimes they are affected by lesions of surrounding structures.
US findings: in myositis the normal, fibrillar structure of the muscles is lost and becomes inhomogeneous, with increased vascularity and sometimes fluid collections (abscess) or calcifications. (Fig. 28, 29, 30, 31)
10. Fibromatosis colli is another muscular lesion which is found in new borns (about three weeks after birth). It presents as swelling of the sternocleidomastoid muscle, usually associated with torticollis.
It is believed to be caused by the muscle trauma (pressure necrosis) during birth.
US findings: on US the affected sternocleidomastoid muscle is swollen, fusiform in the mid portion and the normal structure is altered. It may appear hypo or hyperechoic and one or both heads of the muscle may be involved.
Usually the swelling regress by itself in a few months. (Fig. 32, 33)
Pilomatrixomas are benign skin inclusion cysts associated with hairfollicles.
They are firm,
mobile and painless and develop mainly in the neck area.
US findings: oval, hyperechoic lesions, sometimes with internal calcifications, acoustic shadowing and wall vascularity present. (Fig. 34)
11. Neurofibromas are benign neurogenic tumors that develop from nerve sheaths and are most often associated with Type I Neurofibromatosis. They grow slowly along nerves path and appear as elongated parenchymal lesions. (Fig. 35, 36, 37)
13. Langerhans cell histiocytosis
The bones are the most affected by histiocytosis with the skull being most frequently involved, but also the mandible. That is why a mass in the mandibular area which causes bone destruction must include this diagnosis in its differential.(Fig. 38, 39, 40, 41)
Other bone lesions such as osteomyelitis or bone tumors must also be considered in the differential, but in this cases further imaging is necessary (X-ray, MR or CT).
Congenital vascular malformations are frequently found in the head and neck area. They can be broadly divided into: infantile hemangiomas and vascular malformations (lymphangiomas). Fig. 42, 43, 44.
Lymphangiomas - are congenital lymphatic malformation caused by an abnormal development of the lymph vessels. They are most often found in young children and up to 90% of them occur in the head and neck area.
When found within the posterior triangle of the neck they appear either as one or more large cysts (most frequently) and when found anteriorly as small, numerous cysts, sometimes infiltrating the deeper structures of the neck.
Cystic hygromas can sometimes be very large, affecting various spaces of the neck and causing mass effect on the neck structures. In these situations further imaging is often required (MR, CT)
US findings: poorly delineated, complex cystic lesion, with numerous internal septations, anechoic when uncomplicated or inhomogeneous if hemorrhage occurs.
Doppler interrogation may show vascularity at the level of the internal stroma.