“In children, neck masses usually fall into one of three categories: developmental, inflammatory/reactive, or neoplastic. The history and physical examination can help narrow the diagnosis, with location of the mass being particularly helpful.
Branchial cleft cysts make up approximately 20% of neck masses in children. They commonly present in late childhood or adulthood, when a previously unrecognized cyst becomes infected. They are most frequently found anterior to the sternocleidomastoid muscle, but can also be preauricular.
Thyroglossal duct cysts are located in the midline over the hyoid bone. Frequently, they elevate when the patient swallows.
Dermoid cysts are usually mobile, moving with the overlying skin. They can be located in the submental or midline region.
Thyroid tumors are also usually located in the midline. Malignant masses are usually hard, irregular, non-tender, and fixed.” ABFM
Reference
Evaluation and management of neck masses in children. Am Fam Physician 2014;89(5):353-358.