Salivary gland choristoma of the middle ear: a case report and review of the literature – G.V. Vlasova, P.V. Pavlov, A.Sh. Karimov

The review summarizes the current knowledge on salivary gland choristoma of the middle ear, its clinical manifestations, diagnostics, and features of surgical treatment. Being a form of heterotopia, choristoma represents a histologically normal tissue located in an unusual place, in an organ or region where it is normally absent. According to modern concepts, salivary gland choristoma of the middle ear is a malformation of the second branchial arch. It is formed before the fourth month of fetal development, which probably explains the frequent combination of salivary gland choristoma with developmental anomalies of the stapes, incus, and facial nerve canal. Choristoma is an extremely rare congenital ear pathology with about 50 reports in the scientific medical literature. Choristoma does not have specific clinical symptoms or characteristic CT and MRT features. Therefore, it cannot be diagnosed preoperatively. The only way to verify the diagnosis is pathological assessment. According to the literature data regarding salivary gland choristoma of the middle ear, the disease is more common in women (male to female ratio 1:1.7), and left-sided localization is predominant. The age range at diagnosis is broad, from 3 to 52 years. Manifestations includes conductive hearing loss, otalgia, otorrhea, dizziness, vertigo, tinnitus, facial nerve paresis. Otoscopy reveals a white or yellow-red colored mass behind the intact tympanic membrane. Intraoperative findings show a smooth, dense, lobular mass in the tympanic cavity attached to the horizontal part of the facial nerve canal, dystopia of the canal, dehiscences, malformations of the incus, stapes, and labyrinth openings. The proximity and attachment of choristoma with the facial nerve canal makes its total removal impossible due to the risk of the facial nerve damage in some cases. In these cases, biopsy of the mass, pathological assessment, and further follow-up of the patient are performed. Choristoma is considered to have a favorable prognosis, since there is no tendency to further growth and malignization after surgery. Clinical case. We present a clinical observation of salivary gland choristoma in the tympanic cavity in a 6-yearold boy, quite typical in terms of its clinical manifestations: conductive hearing loss, a mass visualized behind the tympanic membrane, recurrent otalgia. CT of the temporal bones revealed a soft tissue mass in the right tympanic cavity adjacent to the facial nerve canal, dystopia and dehiscence of the fallopian canal. We performed a biopsy of the lesion, followed by pathological examination, as complete removal of the choristoma carried a high risk for facial nerve function. We refrained from revision and reconstruction of the ossicular chain due to the inaccessibility of the posterior parts of the tympanic cavity and dystopia of the fallopian canal. This strategy is not inconsistent with the tactics described in literature. During the 2.5-year follow-up period since surgery, no growth of the mass was observed. The patient currently remains under otorhinolaryngologist supervision. Keywords: choristoma, salivary gland, middle ear, malformation of the middle ear Conflicts of interest. The authors have no conflicts of interest to declare. Funding. There was no funding for this study