A Rare Case of Salivary Gland Choristoma in the Middle Ear with Pharyngeal Hamartoma
Salivary gland choristoma of the middle ear is an extremely rare condition characterized by the presence of normal salivary gland tissue in the middle ear. This benign, slow-growing neoplasm typically involves the ossicular chain and facial nerve, often leading to conductive hearing loss without tympanic membrane (TM) perforation. Histologically, the mass consists of normal salivary gland tissue covered by ciliated columnar epithelium. The condition was first described by Buckmiller et al. in 1961, and since then, only a few cases have been reported in the medical literature. This article presents a detailed account of a rare case of salivary gland choristoma in the middle ear, accompanied by a pharyngeal hamartoma, and discusses the clinical, diagnostic, and therapeutic aspects of this condition.
Case Presentation
The patient was an 8-year-old girl with a 7-year history of suppurative otorrhea in the left ear. She was initially examined by a local otolaryngologist and subsequently referred to our hospital for further evaluation. Clinical examination revealed a normal auricle but a narrow external auditory meatus in the left ear. Otoscopy showed a perforation in the antero-inferior quadrant of the left TM, surrounded by pus. The patient also had a surgical history of pharyngeal hamartoma, which had been excised 7 years prior. No additional abnormalities were noted during the head and neck examination. The patient’s general condition was stable, and there was no family history of similar cases.
Diagnostic Evaluation
Pure tone audiometry revealed a 30-dB conductive hearing loss in the left ear, with normal bone conduction thresholds. A Type B tympanogram was obtained for the left ear, and other laboratory findings were within normal limits. Computed tomography (CT) scans of the temporal bone showed soft tissue density in the left middle ear cavity, tympanic isthmus, and mastoid air cells. A soft tissue mass was identified around the malleus and incudo-stapedial joint, with erosion of the ossicular chain. Notably, the facial nerve canal appeared intact, and no anomalies were observed in the facial nerve.
Surgical Intervention
Based on the 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 was reddish in appearance and appeared to extend anteriorly to the eustachian tube orifice. The mastoid was of the diploic type, and the air cells were filled with granulation tissue. The lesion was also found in the tympanic antrum, blocking the aditus. Consequently, a canal wall-down mastoidectomy was performed. A mass attached to the promontory through a stalk was discovered and easily removed from the malleus handle and TM without risking injury to the facial nerve. Ossicular chain malformations were observed, including an incomplete long process of the incus and an eroded head of the malleus. Ossiculoplasty was performed since the stapes was normal and mobile.
Histopathological Findings
The excised mass measured 20 mm × 5 mm and was covered by white epithelium in the portion extending to the eustachian tube orifice. Histological examination revealed normal salivary gland tissue. Interestingly, the mass was covered by squamous epithelium, a feature rarely reported in cases of salivary gland choristoma. The presence of squamous epithelium was attributed to the perforation of the TM, which may have facilitated the migration of squamous cells.
Postoperative Course
The patient experienced no complications following the surgery. Postoperative pure-tone audiometry showed no significant improvement compared to preoperative results. Otoscopic examination revealed no evidence of recurrence during the 18-month follow-up period.
Discussion
Salivary gland choristoma of the middle ear is a rare condition, with only a handful of cases reported in the literature. It typically presents in the first or second decade of life, with a female predominance. The etiology of this condition remains unclear, but it is thought to be related to congenital anomalous development of embryonic cells. The most common clinical presentation is conductive hearing loss with an intact TM, although our patient presented with suppurative otorrhea and TM perforation, which is unusual.
Extra-Tympanic Anomalies
Patients with salivary gland choristoma often exhibit extra-tympanic malformations in the head and neck region, such as hypoplastic facial features, deformed external ear canals, or other congenital anomalies. In this case, the patient had a history of pharyngeal hamartoma, an extratympanic anomaly not previously reported in association with salivary gland choristoma. This finding suggests that salivary gland choristoma may be accompanied by hamartomas in other regions, not limited to the ear.
Intra-Tympatic Anomalies
The most common intra-tympanic anomalies observed during surgery include ossicular chain erosion and facial nerve involvement. The long process of the incus is frequently shortened, and the stapes is often absent or malformed. Facial nerve involvement can lead to postoperative facial palsy. In our case, the long process of the incus was shortened, and the head of the malleus was eroded, but the facial nerve canal remained intact, allowing for safe removal of the mass without nerve damage.
Surgical Management
Due to the rarity of the condition, salivary gland choristoma is often misdiagnosed preoperatively. Most surgeons opt for exploratory tympanotomy as the initial management plan. Complete removal of the mass is recommended if it can be excised without risking injury to the facial nerve. In some cases, advanced techniques such as KTP laser dissection have been used to remove the mass from the facial nerve. In our case, a retroauricular approach with canal wall-down mastoidectomy was chosen due to the involvement of the mastoid. Although ossiculoplasty was performed, postoperative hearing improvement was not significant, suggesting that a second-stage ossiculoplasty may be necessary in such cases.
Histopathological Features
The histopathological hallmark of salivary gland choristoma is the presence of normal salivary gland tissue within the lesion. The mass typically consists of a compact group of mixed mucous and serous glands in a fibrovascular stroma, covered by respiratory epithelium. In our case, the mass was covered by squamous epithelium, likely due to TM perforation facilitating the migration of squamous cells.
Conclusion
Salivary gland choristoma of the middle ear is a rare condition that can be challenging to diagnose preoperatively. It is often associated with other congenital anomalies in the head and neck region, as demonstrated by the presence of a pharyngeal hamartoma in this case. Surgical management requires careful consideration of the extent of the lesion and potential involvement of the facial nerve. Histopathological examination remains the definitive diagnostic tool. This case highlights the importance of considering salivary gland choristoma in the differential diagnosis of middle ear masses, particularly in patients with congenital anomalies or unusual clinical presentations.
doi.org/10.1097/CM9.0000000000000191
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