Isolated First Branchial Cleft Anomalies of the External Auditory Canal

Background

Branchial cleft anomalies are congenital aberrations that develop from the incomplete obliteration during embryogenesis of the first to fourth pharyngeal pouches. They can result in true fistulae, cysts, or sinus tracts, particularly in the pediatric age group [1].

First branchial cleft anomalies (FBCAs) represent about 5% to 25% of branchial cleft anomalies [1]. FBCAs are usually defined by a smooth, non-tender, fluctuant mass that could involve the parotid gland [2,3] and facial nerve [4,5]. Two types of FBCAs, according to anatomical and histological features, have been identified [6]. Type I includes preauricular masses or sinus tracts localized anteriorly and/or medially to the external auditory canal, laterally to the facial nerve, and are composed only of ectoderm. Type II cysts, with ectoderm and mesoderm, are located at the angle of the mandible and/or submandibular region, lateral or medial to the facial nerve.

The diagnosis of FBCAs can be difficult and depends on radiological and histological findings. In contrast, the required treatment is surgical removal, owing to the high risk of infection or malignancy.

This paper aims to present a rare case of type 1 first bran-chial arch malformative residues in an older woman, with exclusive involvement of the external auditory canal (EAC). Its clinical and histological findings are described and discussed.

Case Report

An 82-year-old woman presented with a history of hearing loss and recurrent otitis media in the last year. She reported ear fullness and swelling in the left EAC, and denied any vertigo or tinnitus. The otomicroscopic examination revealed a cystic mass occluding the left EAC. Pure-tone audiometry showed mixed moderate hearing loss, while the right one showed presbyacusis.

Computed tomography showed soft tissue occupying the EAC without bone erosion signs (Figure 1A, 1B). These findings were confirmed by magnetic resonance imaging, excluding a connection with the facial nerve and parotid gland. Surgical treatment was planned, and excision of the lesion with canaloplasty and a Thiersch graft was performed. This was later found in the retroauricular region, where the surgeon performed a partial-thickness graft harvested with a knife. The skin was then cleaned, keeping only the epithelium and some papillary dermis, and the thin graft was positioned to cover the bony canal.

A histopathological examination revealed a cystic lesion lined by cylindrical epithelium adjacent to the squamous cells. Hence, a diagnosis of type 1 first branchial arch malformative residues was made (Figure 2A–2D).

After 9 months, the patient was disease-free, and pure-tone audiometry showed a mixed moderate hearing loss that did not worsen after surgical treatment. Therefore, she underwent radiological follow-up.

Discussion

FBCA is a congenital condition based on anomalies in the first branchial apparatus that develop into pharyngeal and oral structures [7]. FBCAs are mainly reported in children, and the diagnosis is frequently delayed and associated with a high rate of complications, such as facial nerve paralysis [8]. FBCAs represent 8% of all branchial cleft anomalies. Generally, they result from incomplete obliteration of the clefts that arise between the branchial arches during embryogenesis and are usually located in the neck with other otologic or pharyngeal locations [9,10]. Clinically, FBCAs are characterized by recurrent otor-rhea, pain in the parotid region, or a cervical mass anterior to the sternocleidomastoid [5].

In our case, the onset of the disease was unusual as it began in the patient at the age of 80 years, and symptoms were also uncommon, with swelling of the left EAC, without neck involvement [7]. Despite the patient’s age, no facial nerve involvement was reported. To the best of our knowledge, there are no studies in the literature of cases of a first branchial cleft with the exclusive participation of the EAC [11].

Preoperative imaging is fundamental to determining the anatomic site and possible difficulties during surgery [2]. In our study, magnetic resonance imaging ruled out any potential relationship with the parotid gland and eventual connection with the neck. Still, it did not provide adequate information for a definite differential diagnosis in the presence of puru-lent otorrhea [12]. Moreover, the exclusive EAC involvement ruled out any differential diagnosis with the malignant and benign parotid neoplasms and cysts, parotitis, second bran-chial cleft anomalies, and various pathological entities of the head and neck lymph nodes.

Surgery with total lesion removal was the only possible treatment [13]. A literature review showed that facial nerve lesions are reported in 13% of cases, and the rate of recurrence is about 3%, with a correct diagnosis [2].

In the present case, histopathological examination surprisingly revealed a first branchial cleft cyst due to the presence of cylindric epithelium that was not represented in the EAC. This made possible the differential diagnosis of an epidermoid cyst of the EAC. The cylindric epithelium is located only in the middle ear and not outside when the tympanic membrane is intact.

Moreover, in the present case, the absence of respiratory epithelium and associated lymphoid tissue was fundamental for a differential diagnosis of second branchial cleft cysts.

Conclusions

This is the unique case of type 1 FBCA reported in an adult patient that exclusively involved the EAC. This rare condition represents a potential diagnostic option that should be considered in the differential diagnosis of cysts of the EAC.