Branchial cleft anomalies

Embryology:
Branchial clefts are ectodermal and pouches are endodermal
1st branchial cleft gives rise to eustachian tube, tympanic cavity, mastoid antrum and part of tympanic membrane.
2-5th clefts merge with each other
2nd branchial pouch gives rise to palatine tonsil and tonsillar fossa
3rd branchial pouch gives rise to inferior parathyroid gland, thymus, pyriform sinus
4th branchial pouch gives rise to superior parathyroid gland and apex of pyriform sinus
2-4 branchial clefts form a depression known as cervical sinus of His and branchial cleft cysts probably arise from incomplete obliteration of cervical sinus of His or from epithelial cell rests.

Types:
Sinus, fistula, cyst or any combination
Sinuses: Almost always open externally
Fistula: Fistula between pharyngeal mucosa and neck surface (25%)
Cysts: most common anomaly (75%
Rare: skin tags and cartilages (1%)

General features:
Cysts usually present in older children or young adults
Fistulas usually present in infants or young children
Bilateral anomalies occur in 2%–3% of cases and often familial

First branchial cleft anomaly
Second branchial cleft anomaly
Third branchial cleft anomalies
Fourth branchial cleft anomalies

References:
1. Koeller KK et al. Congenital Cystic Masses of the Neck: Radiologic-Pathologic Correlation. Radiographics. 1999;19:121-146