Middle Ear Lipochoristoma: A Rare Etiology of Hearing Loss

Lipochoristomas are benign tumors composed of mature adipose tissue originating from mesenchymal elements of the vestibulocochlear nerve (CN VIII). They account for only 0.1% of tumors in the internal auditory canal (IAC) and cerebellopontine angle (CPA). Most patients present with hearing loss (HL), tinnitus, and dizziness due to CN VIII involvement. ¹ These symptoms overlap with other retrocochlear lesions, including schwannoma and meningioma. Hearing preservation after resection is generally unsuccessful, as the tumor is often intimately associated with the auditory nerve. ² Here, we present the first reported case of middle ear lipochoristoma in an adult. This case was deemed exempt by the Medical College of Wisconsin Institutional Review Board and written informed consent was obtained for publication of patient information and images.

Case Report

A 68‐year‐old male with no significant prior otologic history presented with 4 months of left‐sided otorrhea, aural fullness, and HL. Otomicroscopy demonstrated a polyp‐like growth on the tympanic membrane (TM) and associated discharge. Ototopical therapy provided incomplete resolution, prompting imaging.

A computed tomography (CT) scan demonstrated extensive opacification of the left middle ear and mastoid, ossicular erosion, and a small tegmen tympani dehiscence suggestive of cholesteatoma (Figure 1). Given these findings, tympanomastoidectomy was performed. A preoperative audiogram revealed moderately severe to severe mixed HL in the left ear and mild to moderate sensorineural hearing loss (SNHL) in the right ear.

Figure 1.

Temporal bone CT findings. Axial (A) and coronal (B) CT images of the left temporal bone showing middle ear and mastoid opacification with ossicular erosion (A) and a 1.3 mm tegmen dehiscence (B). CT, computed tomography.

Intraoperatively, the TM had a retraction pocket but no cholesteatoma. The middle ear was filled with dense granulation tissue resembling an encephalocele, adherent to the TM and promontory. The mass was unresponsive to facial nerve stimulation. The malleus, incus, and stapes superstructure were severely eroded, requiring removal of the incus and malleus. A mastoidectomy with zygomatic root drill‐out identified a small linear tegmen tympani dehiscence, which was repaired, though the mass was not attached to this area. After confirming no stimulation, the mass was resected. Histopathologic evaluation revealed features consistent with lipochoristoma, including nerve bundles, fibrous tissue, blood vessels, fat, and calcifications. Immunostaining for S100 and Glial Fibrillary Acidic Protein (GFAP) confirmed neural tissue, supporting the diagnosis (Figure 2). This was further validated on send‐out analysis.

Figure 2.

Histologic and immunohistochemical findings. H&E staining shows nerve bundles, fibrous tissue, fat, and calcifications at ×10 (A) and ×20 (B). S100 (C) and GFAP (D) immunostaining confirm neural tissue. GFAP, glial fibrillary acidic protein; H&E, hematoxylin and eosin.

Six months later, the patient underwent ossicular chain reconstruction without evidence of recurrence. Despite prosthesis placement, mixed HL persisted, and he was fitted with hearing aids for effective rehabilitation. He continues to undergo surveillance MRI to monitor for potential regrowth.

Discussion

Lipochoristomas are rare and diagnostically challenging due to nonspecific symptoms and resemblance to other otologic conditions like cholesteatoma and vestibular schwannoma. In this case, CT and surgical findings suggested cholesteatoma, while the mass resembled an encephalocele. Definitive identification relied on histopathology and immunohistochemical staining, highlighting the crucial role of pathology in distinguishing lipochoristomas from other middle ear lesions.

Lipochoristomas are typically found in the IAC or CPA, where they present with nonspecific symptoms. HL is the most common presenting symptom, followed by tinnitus, dizziness, and vertigo, with less frequent reports of headache and facial paresthesia. ² , ³ HL outcomes vary, with some patients experiencing SNHL, while others have no impairment. Although complete surgical resection generally prevents recurrence, SNHL is a frequent postoperative complication. ¹

Surgical management is challenging due to the tumor's proximity to critical structures like the auditory nerve and ossicular chain. As a result, treatment for tumors in the IAC and CPA has shifted from complete excision to more conservative approaches focused on nerve preservation. ¹ In this case, HL was primarily conductive from ossicular disruption. The mass was successfully excised without recurrence at follow‐up, but subsequent surgical hearing rehabilitation remained suboptimal, partly due to underlying age‐related SNHL. However, the patient did experience significant benefit with amplification.

While this case represents the first reported instance of lipochoristoma in the middle ear, previously reported cases may have been misclassified as lipomas. Wu et al first suggested that “lipochoristoma” more accurately describes this tumor composed of fat with fibrous, vascular, or muscular elements, unlike lipoma, which contains only fat. ¹ A search for “middle ear lipoma” identified 17 cases, many misdiagnosed as cholesteatomas, similar to our patient's preoperative diagnosis. Only three of these were in adults. ⁴ Whether these were true lipochoristomas is unclear. Accurate terminology is essential for diagnosis, treatment, and reporting, and should be standardized to improve consistency in the literature.

Author Contributions

Oliwia W Mlodawska, BS, collected clinical data, conducted literature review, drafted the manuscript, and created the figures; Karl W. Doerfer, MD, provided guidance on case interpretation and reviewed the manuscript.

Disclosures

Competing interests

Karl W. Doerfer is the Consultant for Advanced Bionics and Stryker.

Funding source

None.