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Subcutaneous/Foreign Bodies 

Subcutaneous Mass looks for lumps in any part of the body 

How the Test is Performed

Ultrasound is a painless method that uses sound waves to create images of the inside of the body. For lumps in your neck you will lie with your neck extended beyond its usual limit (hyperextended). The ultrasound technician will place a gel onto your neck. Next, the technician will move a transducer, over the area.
The transducer gives off sound waves. The sound waves go through the body and bounce off the area being studied (in this case, the thyroid gland). A computer looks at the pattern that the sound waves create when bouncing back, and creates an image.

How to Prepare for the Test

No special preparation is necessary for this test.

How the Test Will Feel

You should feel very little discomfort with this test. The gel may be cold.

Why the Test is Performed

Lymph nodes 

An enlarged cervical lymph node is the most commonly encountered neck lump. The role of ultrasound is to differentiate pathological nodes (e.g., metastases, lymphoma, tuberculous lymphadenitis) from normal/reactive nodes. Different ultrasound criteria have been established to differentiate benign from malignant cervical lymph nodes. 3 No single criterion is an absolute indicator for predicting malignant nodal disease, and all known ultrasound criteria should be applied together. These signs may point to a specific diagnosis or help determine which lymph node to sample using ultrasound-guided FNAC.
Size alone is a poor criterion. Among the various measurement parameters for nodal size, minimum axial diameter is the most specific dimension for predicting malignancy. Van den Brekel et al recommend a minimum axial diameter of 7 mm for submental/submandibular nodes and 8 mm for other cervical nodes.4 They cite an overall accuracy of 70% when minimum axial diameter is used as a sole diagnostic criterion. If ultrasound examination of a patient with head and neck cancer reveals a lymph node that is increasing in size or new nodes, then these findings should be viewed with a high degree of suspicion.

Malignant lymph nodes are commonly round, while benign nodes tend to have an elliptical shape.5-7 Axis ratios (either short/long or long/short) can be measured, though a visual qualitative assessment is usually sufficient.

The presence of an echogenic hilus within a cervical lymph node reflects preserved sinusoidal architecture and is a good sign for predicting benignity.8,9 The presence of a round node with an absent hilus is highly indicative of malignancy.

A diffusely hypoechoic, or pseudocystic, enlarged lymph node has previously been described as a sign of lymphoma. Newer generation transducers, however, more commonly show a reticulated intranodal pattern.10,11

In patients with primary squamous cell carcinoma (SCC), the presence of necrosis (coagulative and cystic) within an enlarged lymph node is a very strong indicator of malignancy.12 Tuberculous nodes and metastases from papillary thyroid carcinoma also tend to undergo cystic degeneration,13 and these may mimic metastatic nodes from SCC. An ill-defined border or frank invasion of neighboring structures can be detected easily with ultrasound and indicates poor prognosis.

On color Doppler imaging, the distribution of vessels within a node is more reliable than various vascular and resistive indices.14 Benign nodes have a central hilar flow pattern, whereas malignant nodes have a disorganized peripheral pattern. Areas of relative avascularity reflect the presence of necrosis and peripheral subcapsular vessels.

The typical small punctate calcification seen in a papillary thyroid carcinoma is also observed in lymph node metastases from papillary carcinoma.18 The sign is specific and should prompt a diligent search for the thyroid primary.

Branchial cleft cyst

Ninety-five percent of all branchial cleft anomalies arise from remnants of second branchial apparatus. Second branchial cleft cysts are most common in children and young adults, and the anatomic location is one of the best clues for diagnosis. These cysts are generally found superficial to the common carotid artery and internal jugular vein, posterior to the submandibular gland, and along the medial and anterior margin of the sternocleidomastoid muscle.
Appearance on ultrasound depends on whether there is any previous infective or hemorrhagic component.19 Most uncomplicated branchial cleft cysts appear as well-circumscribed round/ovoid anechoic masses with thin walls and posterior acoustic enhancement. Some cysts may exhibit a pseudosolid appearance due to the presence of cellular material and cholesterol. Previous episodes of infection or hemorrhage may cause the lesions to appear ill defined and thick walled, with septae and heterogeneous internal echoes (Figure 2). Lesions with this appearance should be differentiated from metastatic lymph nodes. Further evaluation will require ultrasound-guided FNAC.

Thyroglossal duct cyst

This congenital anomaly is related to the thyroglossal duct. Most lesions are anatomically related to the hyoid bone. About 25% to 65% occur in the infrahyoid neck, 15% to 50% occur at the level of the hyoid, and 20% to 25% are suprahyoid. Thyroglossal duct cysts are characteristically located in the midline of the anterior neck above the thyroid cartilage. The cysts are slightly off midline and deep to strap muscles at the level of thyroid cartilage.
Thyroglossal duct cysts typically appear on ultrasound as well-defined thin-walled anechoic cysts with posterior acoustic enhancement. They may have a uniformly pseudosolid echo pattern similar to branchial cleft cysts, owing to proteinaceous content. Previous infection or hemorrhage can result in a heterogeneous appearance.

The role of ultrasound in patients diagnosed clinically with a thyroglossal duct cyst is to confirm diagnosis and the cyst's relation to the hyoid bone, to detect internal solid components suspicious for malignancy, and to detect the presence of normal thyroid tissue in the neck. If the only functioning thyroid tissue is contained within the thyroglossal duct cyst, then surgery may result in hypothyroidism.20

Lipoma

This benign encapsulated fatty lesion is typically subcutaneous or submucosal in location. About 13% of all lipomas occur in the head and neck. The typical appearance on ultrasound is a well-defined compressible avascular/hypovascular hypoechoic mass with linear echogenic streaks parallel to the transducer 

Nerve sheath tumor 

Schwannoma and neurofibroma are the most frequently encountered nerve sheath tumors in the head and neck. Common sites in the neck include the vagus nerve, ventral and dorsal cervical nerve roots, cervical sympathetic chain, and brachial plexus. Nerve sheath tumors appear as well-defined solid heterogeneous hypoechoic masses on ultrasound (Figure 5). The presence of a thickened nerve continuous with the mass is the best clue.22 The nerve sheath tumor is typically hypervascular on power Doppler examination.

Venous vascular malformation

Approximately 15% of venous vascular malformations occur in the head and neck region. Malformations appear as well-defined heterogeneous hypoechoic masses on ultrasound. Multiple sinusoidal spaces containing slow-flowing internal echoes are also seen (Figure 6).23 The presence of phleboliths (small echogenic foci with posterior acoustic shadowing), seen in about 20% of cases, essentially confirms diagnosis.

 

Foreign Body

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