A rare case of salivary gland choristoma in the middle ear with pharyngeal hamartoma

Field: Medicine (Health Sciences)

To the Editor: Salivary gland choristoma of the middle ear is a normal salivary gland tissue located in the middle ear. It is a benign and slow growing neoplasm that usually involves the ossicular chain and facial nerve,[1,2] and most of the patients usually suffer from conductive hearing loss without tympanic membrane (TM) perforation. The histological feature consisted of normal salivary gland tissue with a mass covered by ciliated columnar epithelium. To the best of our knowledge, it was first described by Buckmiller et al.[3] We presented a rare case of salivary gland choristoma in which the patient had a history of hamartoma in the pharynx and the mass was covered by squamous epithelium. An 8-year-old girl with 7 years history of suppurative otorrhea in the left ear was examined by her local otolaryngologist. She was referred to our hospital for further investigation. Examination revealed a normal auricle, but a narrow external auditory meatus of the left ear. On otoscopy, a perforation was observed in the antero-inferior quadrant of the left TM, surrounded by a lot of pus. The patient also had a surgical history of pharyngeal hamartoma, which was done in a local otorhinolaryngological department 7 years ago. There were no additional specific findings in head and neck examination. The patient's general condition was fine, and there was no similar case in her family previously. The results of pure tone audiometry revealed a 30-dB conductive hearing loss with normal bone conduction thresholds in the left side. Type B tympanogram was obtained for the left ear, and results of other laboratory examinations were within normal limits. In the computed tomography scan of temporal bone, soft tissue density was observed in the left middle ear cavity, tympanic isthmus and mastoid air cells [Figure 1]. Furthermore, a soft tissue mass around the malleus and incudo-stapedial joint was identified with the ossicular chain eroded, and no anomalies in the facial nerve were noted [Figure 2].Figure 1: Axial CT-scan views. (A) The left middle ear cavity, tympanic isthmus, and mastoid air cells are filled with soft tissue. The malleus and incudostapedial joint are affected. (B) The canal wall of the facial nerve is intact.Figure 2: Histology shows the mass including normal salivary gland tissue, as well as sebaceous glands, hair follicle, some fat tissue, and vascular tissue (H&E, original magnification ×20;A). The mass is covered by squamous epithelium (H&E, original magnification ×200; B).With a presumptive diagnosis of cholesteatoma, a left mastoidectomy was planned under general anesthesia. A retroauricular surgical approach was chosen and the mass within the tympanic cavity was exposed. The mass fully filling the cavity was reddish in appearance and seemed to extend anteriorly to the eustachian tube orifice. The mastoid was depliotic type and the air cells in the mastoid were filled with granulation tissue. The lesion tissue was also found in the tympanic antrum, blocking the aditus. As a result, canal wall-down mastoidectomy was performed, and a mass attached to the promontory through a stalk was discovered. The entire mass was easily removed from the malleus handle and the TM without any risk of injury to facial nerve. After the removal of the lesion, ossicular chain malformations were also observed: the long process of the incus and the head of the malleus was incomplete. Ossiculoplasty was then performed because the stapes was normal and moved well. The elastic mass was 20 mm × 5 mm in size, and the portion that extended to the eustachian tube orifice was covered by white epithelium. There were no complications after the operation. The results of postoperative pure-tone audiometry showed no significant improvement compared with preoperative data. Otoscopic examination showed no evidence of recurrence in the following 18 months after the initial surgery. The histologic examination revealed normal salivary gland tissue. In addition, we observed the mass was covered by squamous epithelium, which was very rare in the reported features. Salivary gland choristoma of the middle ear was first described in 1961.[3] Since then very few cases have been described. Salivary gland choristoma in the middle ear usually occurs during the first and second decades of life with a female preponderance. Their origin is unknown, but they seem to be related to the congenital anomalous development of embryonic cells.[4] The extra-tympanic malformations in salivary gland choristoma patients were frequently in the head and neck region, including a hypoplastic face or pinna, a deformed external ear canal, and so on. In our case, the patient had a history of pharyngeal hamartoma, which was a new extratympanic anomaly never reported before. The predominant complaint of the patients was hearing loss with an intact TM on otoscopy, however, our patient's chief symptom was discontinuous otorrhea since infancy, which was similar to one patient reported by Saeger et al.[5] We presumed that the mass extended to the eustachian tube orifice, which affected the air ventilation between the tympanic cavity and outer space, so that it was easier to cause suppurative otorrhea and perforation of the TM. Our report further improved that not all the patient's TM was intact, and suggested that salivary gland choristoma of the middle ear might be accompanied by extra hamartoma in the pharynx, and not only the anomalies in the ear. The most common intra-tympanic anomalies observed in the operation were ossicular chain erosion and involvement of facial nerve. The shortening of long process of the incus was most frequently reported, and the stapes was usually absent or malformed. The facial nerve was frequently involved, causing facial palsy in some patients after the surgery.[6] In our patient, we observed that the long process of the incus was shortened and the head of the malleus was also eroded, however, the canal of the facial nerve was still completed, so that we could move the whole mass easily without any damage to the facial nerve. Because choristoma of the middle ear could not be diagnosed before operation, most surgeons preferred an exploratory tympanotomy as an initial management plan, and complete removal was recommended when the mass was easy to excise without any risk to the facial nerve. There is also a report in which the author introduced the KTP laser to dissect the mass from the facial nerve.[7] We chose the retro-auricular surgical approach, and the canal wall-down mastoidectomy was performed because the mastoid was affected by the mass, which was similar to some patients reported.[8,9] However, the post-operative hearing result revealed no significant improvement, we suggested that ossiculoplasty should be done in the second stage. The histopathologic feature of salivary gland choristoma of the middle ear was normal salivary gland tissue in the lesion. The mass was composed of a compact group of mixed mucous and serous glands in a fibro-vascular stroma, covered by the respiratory epithelium. In our case, the mass was covered by the squamous epithelium, and we supposed that it might be due to the perforation of the TM, causing the migration of the squamous epithelium. Salivary gland choristoma of the middle ear is a rare disease which may be confused with other middle ear mass. Currently, the only means to establish a diagnosis of the choristoma is by microscopic examination. Some patients may be accompanied by other hamartoma in the head and neck region, and caution is required when there is perforation in the TM. Declaration of patient consent The authors certify that they have obtained the patient consent form. In the form, the patient's parents have given their consent for her images and other clinical information to be reported in the journal. The patient understands that her name and initials will not be published and due efforts will be made to conceal her identity but anonymity cannot be guaranteed. Conflicts of interest None.