A 30-year-old man comes in for an evaluation of exostoses. He previously consulted another otolaryngologist who told him that he had exostoses blocking his ear canal. On examination, a mass was found that completely blocked the outer ear canal. Attempts to move the mass and see what's behind it were not successful. The mass appeared to be primarily based on the anterior external auditory canal skin, though it did not involve the skin. The audiogram showed a mild conductive hearing loss in the left ear. The patient's medical history was significant for neuroblastoma as a child and some type of thyroid tumor.
The mass looked like a smooth, circular, and soft lesion. It had the signs and symptoms of a benign mass. However, an intact skin does not necessarily rule out malignancy. Squamous cell carcinoma of the external auditory canal starts at the skin level and often presents with a fleshy mass that may easily bleed and cause chronic ear drainage. Other cancers of the ear canal may present subcutaneously, with normal-looking skin over the mass. These cancers include adenoid cystic carcinoma, among others. In rare cases, parotid malignancies may spread through the small fissures of the anterior external auditory canal and present as an ear canal mass. In general, if a mass is subcutaneous, then imaging should be obtained first before performing a biopsy of the lesion. This is especially true for a middle ear mass. Very rarely, an anomalous carotid artery can present as a middle ear mass and a biopsy would prove disastrous for the patient.
The imaging to be obtained in a patient with an ear canal mass includes CT of temporal bones without contrast to evaluate for bony destruction and MRI with and without gadolinium (contrast) to evaluate the nature of the mass and its extent. CT of temporal bones with and without contrast is rarely indicated and subjects the patient to a double dose of radiation, as the CT has to be repeated after the contrast is given. Alternatively, an MRI could be obtained first and, depending on its results, a CT scan could be ordered. However, if surgery is to be planned, the information from the CT scan is very valuable in identifying any bony destruction.
This patient got a CT scan of the temporal bones and an MRI of the internal auditory canals with and without contrast. Because the mass completely obstructed the ear canal, we opted to obtain the CT upfront considering that surgery was necessary to relieve the obstruction. The CT of the temporal bones showed that the mass was only obstructing the cartilaginous canal and did not involve the bony external auditory canal (Fig. 2). The MRI found the mass to be well circumscribed and did not involve the parotid gland (Figs. 3 and 4).
The patient underwent a transcanal removal of the mass. Intraoperatively, the mass was found to be well encapsulated. A frozen section biopsy of the lesion showed neurofibroma, a benign tumor of the covering of the nerves (nerve sheath).
While isolated neurofibromas do occur, clinicians should be alerted to the possibility of neurofibromatosis when presented with a diagnosis of neurofibroma after excising a mass. Neurofibromatosis is a family of genetic disorders that can lead to the development of multiple tumors.
Neurofibromatosis type 2 (NF2) is an autosomal dominant genetic disorder caused by a mutation on chromosome 22 that predisposes a person to the growth of multiple tumors, including bilateral vestibular nerve schwannomas (acoustic neuromas), meningiomas, ependymomas, and other cranial nerve schwannomas, among others. Bilateral vestibular schwannomas are seen in 90 percent of patients with NF2, while 50 percent these patients develop meningiomas or tumors in other cranial nerves and 50 percent develop spinal lesions. Majority of the patients also exhibit juvenile subcapsular cataract (opacity of the eye lens).
The MRI of this patient's internal auditory canals showed no cranial nerve or intracranial tumor, which makes the possibility of NF2 close to zero.
Neurofibromatosis type 1 (NF1) is a disorder caused by a mutation on chromosome 17 that can cause multiple cutaneous neurofibromas. Patients with any two of the following are considered to have NF1: have six or more café-au-lait spots (light brown spots that are larger than 5 mm), more than two axillary (underarm) or inguinal freckles, two or more neuro-fibromas or one plexiform neurofibroma, optic nerve glioma, two or more iris hamartomas (Lisch nodules), sphenoid dysplasia, or long-bone abnormalities such as pseudarthrosis. Other diagnostic criteria include having a first-degree relative with NF1 in addition to any one of the above conditions.
Patients with NF1 are at risk of developing tumors in other tissues that develop from neural crest cells—embryonic cells that differentiate into multiple cell types like Schwann cells, medullary cells of the adrenal gland, among others.
Looking back at the patient's medical history that includes tumors of the adrenal gland (neuroblastoma) and thyroid gland (likely medullary cancer), it becomes clear that this patient suffers from NF1. While this diagnosis does not necessarily change the management of the patient's ear canal tumor, it is important for the purpose of family planning, genetic counseling, and medical evaluation of his first-degree relatives and off-springs.
BONUS VIDEOS: VISUAL DIAGNOSIS
Read this month's Clinical Consultation case, then watch the accompanying videos from Hamid R. Djalilian, MD, to review the patient's imaging for yourself.
- Video 1. Axial CT of the temporal bones showing the mass blocking the ear canal https://journals.lww.com/thehearingjournal/Pages/videogallery.aspx?videoId=12.
- Video 2. Coronal (vertical) CT of the temporal bones showing that the mass does not involve the ear canal bone https://journals.lww.com/thehearingjournal/Pages/videogallery.aspx?videoId=11.
- Video 3. Sagittal (looking from inside coming out) CT of the temporal bones showing the mass and its relationship to the auricle and canal https://journals.lww.com/thehearingjournal/Pages/videogallery.aspx?videoId=10.
- Video 4. Axial T1-weighted post-gadolinium enhanced MRI showing the mass in the outer canal https://journals.lww.com/thehearingjournal/Pages/videogallery.aspx?videoId=9.
- Video 5. Coronal T1-weighted gadolinium-enhanced MRI of the IAC showing the mass and its location https://journals.lww.com/thehearingjournal/Pages/videogallery.aspx?videoId=8.
- Video 6. Axial T2-weighted MRI showing isointense mass (similar color to brain) https://journals.lww.com/thehearingjournal/Pages/videogallery.aspx?videoId=7.
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