"cyst: no internal or external communication"
"fistula: communicates both internally and externally"
"first branchial cleft anomalies (5-8%) 1-8: seen above the level of the mandible near the external auditory canal within or close to the parotid gland."
"The anomalies result from branchial apparatus (six arches; five clefts), which are the embryologic precursors of the ear and the muscles, blood vessels, bones, cartilage, and mucosal lining of the face, neck, and pharynx 1."
"Cysts are the most common, outnumbering fistulas and sinuses ~2:1 6. Among fistulae and sinuses, the order prevalence is thought to be: external draining sinus > complete fistula > internal draining sinus 6; although some anomalies can occur in combination."
"The anomalies result from branchial apparatus (six arches; five clefts), which are the embryologic precursors of the ear and the muscles, blood vessels, bones, cartilage, and mucosal lining of the face, neck, and pharynx 1."
"During the 3rd to 5th week of embryonic development, the second arch grows caudally and covers the third, fourth and sixth arches. When it fuses to the skin caudal to these arches, the cervical sinus is formed. Eventually, the edges of cervical sinus fuse and the ectoderm within the tube disappears 9. Persistence of branchial cleft or pouch results in a cervical anomaly located along the anterior border of the sternocleidomastoid muscle from the tragus of the ear to the clavicle 10."
"necrotic lymph node metastases (e.g. from squamous cell and papillary thyroid carcinomas)"
"infectious adenitis (e.g. tuberculosis)"
"vascular lesion on non-enhanced CT images (e.g. mycotic aneurysm)"
"neurogenic tumours with cystic degeneration (e.g. schwannomas)"