Yee-Hyuk Kim, MD, PhD First Published January 30, 2019 Other
https://doi.org/10.1177/0145561318824808
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Article first published online: January 30, 2019
Yee-Hyuk Kim, MD, PhD1
1Department of Otorhinolaryngology—Head and Neck Surgery, School of Medicine, Catholic University of Daegu, Daegu, Korea
Corresponding Author: Yee-Hyuk Kim, MD, PhD, Department of Otorhinolaryngology—Head and Neck Surgery, School of Medicine, Catholic University of Daegu, 33, Duryugongwon-ro 17-gil, Nam-gu, Daegu, 42472 Korea. Email: yhukim@cu.ac.kr
Schwannoma is a benign neoplasm that originates from Schwann cells. Here, I present the first reported case of schwannoma occurring in the posterior wall area of the ear canal, accompanied by definitive mastoid bone erosion.
The left ear canal entrance of a 23-year-old female patient was blocked by a mass, and the tympanic membrane was unobservable (Figure 1). Pure-tone audiometry showed an air-conduction hearing threshold of 50 dB and bone-conduction hearing threshold of 12 dB in the left ear. Temporal bone computed tomography (CT) showed soft tissue density across the posterior wall of the external auditory canal, postaural region, and mastoid along with clear destruction of the mastoid cortical bone and air cells (Figure 2). The transmastoid approach was used to remove the tumor spanning the mastoid, postaural region, and external auditory canal. The tumor was completely removed without fragmentation and measured approximately 3.5 cm × 3.5 cm. After the tumor removal, the lost lateral bony region of the external auditory canal and the entire posterior surface of the cartilaginous portion had to be reconstructed. The tragal cartilage was harvested and divided into 2 pieces and then placed along the natural curvature of the external auditory canal prior to fixation. A hole was created in the remaining bony region of the external auditory canal with a surgical drill after tumor removal, and then the tragal cartilage was fixed onto the bony region of the external auditory canal (Figure 3). A full-thickness skin graft was performed over the tragal cartilage and entrance of the external auditory canal (region in which the skin was lost after tumor removal) with skin obtained from the postaural region (Figure 4). To prevent posterior displacement of the transplanted tragal cartilage, the cortical bone plate of the mastoid was used for support (Figure 4). Ear canal examination and temporal bone CT performed at 8 months after surgery revealed that the reconstruction of the external auditory canal was successful; the external auditory canal was open and wide (Figure 5). The pneumatization of the mastoid was well maintained (Figure 6), and the ability to hear from the left ear improved to a normal state.
Figure 1. A mass blocking the opening of the ear canal was observed on otoscopic examination.
Figure 2. In the axial view of temporal bone computed tomography (CT) scan, soft tissue shadows were observed in the posterior wall of the ear canal and the postauricular and mastoid areas, while destruction of the mastoid cortical bone and air cells was also observed.
Figure 3. A drill was used to create a hole in the remaining bony area of the ear canal, and the tragal cartilage was fixed on the bony area of the ear canal by suturing the tragal cartilage with stitches (arrows: suture locations).
Figure 4. A full-thickness skin graft was performed on the area of the ear canal defect lateral to the grafted tragal cartilage, and a harvested mastoid cortical bone plate was used to support the grafted tragal cartilage from behind (arrow: results of a full-thickness skin graft; arrow head: mastoid cortical bone plate).
Figure 5. The ear canal that had been blocked by the mass was reopened through the ear canal reconstruction after removal of the mass.
Figure 6. The reconstructed ear canal and pneumatized mastoid cavity are observed on the temporal bone CT scan. CT indicates computed tomography.
Histopathological tests, particularly hematoxylin and eosin staining, revealed that spindle cells were densely packed in a palisade or whirling pattern, and both the nucleus and cytoplasm tested positive for S-100 protein with immunohistochemical staining; based on these results, the tumor was diagnosed as a schwannoma. There were no findings indicative of malignancy. To date, 2 years after the surgery, there have been no signs of tumor recurrence.
Schwannomas generally do not invade surrounding tissues.1,2 However, wide bone invasion was observed in the mastoid in the current case. Schwannoma bone invasion has only rarely been reported. Bone erosion from an extraosseous tumor is believed to be caused by pressure from the gradually growing mass despite the benign nature of the tumor.3,4
Declaration of Conflicting Interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) received no financial support for the research, authorship, and/or publication of this article.
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