December 2012 - Dr. Stephanie Petkiewicz
Clinical history: 36 year old male with a recurrently infected pre-auricular sinus tract.
First Branchial Cleft Cyst-Type II
Histogenesis: Remnant of an incompletely involuted branchial cleft, arch or pouch. The cysts arise on the lateral neck anywhere from adjacent to the ear to the anterior border of the sternocleidomastoid in the inferior neck. These sites represent the location of one of the four branchial clefts. Structures derived from first branchial cleft include the incus, malleus, mandible, anterior 2/3 of tongue, sublingual and submandibular glands, Eustachian tube, tympanic cavity and membrane, mastoid air cells, external auditory canal and a portion of the pinna.
Clinical Features: The residual branchial clefts present as cysts, sinuses or fistulae. Males and females are equally affected and the lesions are bilateral in 2-10% of patients. Usually the branchial cleft defect is the only developmental anomaly, however, rarely they may be associated with other defects such as a hearing problems, preauricular pits, or tear duct atresia. Occasionally sinuses from branchial clefts present as cysts and will be partially removed surgically, but the remaining tissue will grow back to again form a recurrent cyst/sinus.
Histological features: First branchial cleft cysts are of two varieties, type I and type II. Type I cysts are lined by keratinized stratified squamous epithelium and represent a duplication of the membranous external auditory canal, thereby containing only ectodermal elements. There are no adnexal structures associated with a type I cyst. There may be a fistula or sinus tract draining the cyst. Parotid tissue may be associated with the tract. Type II cysts contain both ectodermal and mesodermal tissues, thus the cyst or tract will contain adnexal structures as well as cartilage. The type II cysts represent an embryologic duplication of the pinna and auditory canal. The parotid gland and auditory canal may be involved by the sinus tract.
Second branchial cleft cysts arise along the anterior border of the sternocleidomastoid and are more common than 1st cleft cysts. These cysts may be lined by stratified squamous epithelium, respiratory epithelium or both. In most cases there is lymphoid tissue in the wall which may form germinal centers. Additionally, there may be recurrent infection of the cyst leading to fibrosis of the wall and replacement of the cyst lining by granulation tissue.
Third branchial cleft cysts are rare and they arise around the laryngeal ventricle. The cysts are lined by stratified squamous epithelium.
Fourth branchial cleft cysts have only been reported 1-2 times. Should they arise, they would have openings along the anterior border of the lower portion of the sternocleidomastoid and the tract would run beneath the subclavian artery or the aortic arch and then return to the neck, ending adjacent to the esophagus.
Differential diagnosis: First branchial cleft cysts may be confused with epidermal inclusion cysts or dermoid cysts if the lesion contains or does not contain adnexal structures, respectively. History and the presence of a sinus tract may help distinguish these diagnoses. Additionally, the presence of cartilage in a first branchial cleft cyst eliminates the possibility of a dermoid cyst. Metastatic squamous cell carcinoma with cystic degeration in a cervical lymph node may be misdiagnosed as a second branchial cleft cyst, however, the absence of severe atypia and the presence of lymphocytic infiltrates may guide the diagnosis towards branchial cleft cyst.
This Case: This is a First Branchial Cleft Cyst, Type II. The sinus tract is seen in image B. The cystic component is lined by keratinizing stratified squamous epithelium with attached adenexal structures (hair follicles and sebaceous glands). Images B and E demonstrate the presence of cartilage. All of these histological features as well as the history of a pre-auricular sinus are consistent with the above diagnosis.