A 70-year-old patient presents with a history of right-sided hearing loss and blockage. He states that he has had this problem for three years. He is otherwise healthy with no other significant medical problems. On examination, he is found to have a fleshy mass in the anterior cartilaginous external auditory canal. When this is pointed out, he states that it has been biopsied two previous times and was found to be benign. Examination medial to the mass shows that the ear canal is filled with keratin (dead skin) debris. He has recently been having some pain in that ear as well. A picture of his examination can be seen to the right.
Diagnosis: Squamous Cell Carcinoma
When a patient presents with an ear canal mass and accompanying pain, the suspicion for cancer should be high. If biopsies turned up negative in the past, it may sway the clinician to not pursue this further. However, the clinician should always make his or her own assessment at the time that patient presents with certain symptoms. Disease courses change with time, and the quality of any pathological diagnosis is dependent on the quality of the specimen. Because of the very small space in the ear canal, its vascular nature, and the additional factor of small instrumentation related to the ear, biopsy specimens of the ear canal are usually small and do not provide the pathologist the necessary volume of tissue needed to make the proper diagnosis. This leaves the patient in a difficult situation where the disease process continues while the surgeon is hesitant to intervene because of the absence of a diagnostic pathologic specimen.
The differential diagnosis for an ear canal mass is long. However, the diagnosis of keratosis obturans given by the pathologists and radiologist is incorrect for several reasons. Keratosis obturans is a condition that is generally present for most of the patient's lifetime and would not suddenly start at the age of 70. It is caused by an abnormality in the migration of the keratin debris of the ear canal, which leads to accumulation of the keratin in the ear canal with obstruction. There is no soft tissue mass associated with the presence of this condition. The diagnosis cannot be made when there is a mass blocking the natural outward migration of the keratin (dead skin) in the ear canal, as naturally occurs. In addition, keratosis obturans is commonly associated with recurrent respiratory infections, which was not present in this patient.
Finally, keratosis obturans is a condition where both ear canals are typically affected; it would be unusual to occur on only one side. A pathologist had previously made the diagnosis of canal cholesteatoma. However, external auditory canal cholesteatoma occurs in the bony canal and not in the cartilaginous ear canal. In addition, bony destruction of the ear canal is required as part of the external auditory canal cholesteatoma diagnosis, which was not present.
This patient had another biopsy performed in the office that again returned as benign. CT scan of the temporal bone showed no bony canal destruction, which likely represented a benign process. Unconvinced, we performed a fourth biopsy that showed squamous cell carcinoma.
Squamous cell carcinoma of the external auditory canal is a rare tumor that can occur from chronic irritation of the ear canal from chronic external otitis. It can also occur from invasion of a lateral canal squamous cell carcinoma that subsequently invaded the external auditory canal. Occasionally, it occurs for no apparent reason.
When diagnosed early, the cancer is highly treatable, with cure rates reaching 95 percent. However, because of the close proximity of the durra, tympanic membrane, the middle ear, and the large vasculature below and anterior to the middle ear such as the carotid and jugular vein, a somewhat more advanced tumor can be incurable. Fortunately, the ear canal bone forms a strong barrier for cancer spread. If that barrier is breached, however, the cancer can metastasize rapidly. Once the cancer reaches the mastoid air cells, it easily spreads within the air cell system and quickly breaks down the small bony septations of the mastoid. Invasion of the facial nerve is not uncommon in advanced temporal bone squamous cell carcinoma, given that it is only 2 mm to 3 mm from the ear canal at the level of the annulus of the tympanic membrane.
Treatment of temporal bone squamous cell carcinoma is primarily surgical resection. A tumor limited to the bony external auditory canal with minimal bony destruction can be easily resected with a lateral temporal bone resection that involves removing the ear canal in its entirety, the tympanic membrane, the malleus, and incus. While highly effective at curing the cancer, this usually leaves the patient with a significant conductive hearing loss.
In the last five years, we have started performing a tympanic membrane sparing lateral temporal bone resection to preserve conductive hearing while fully respecting the cancer. In a small series of patients whose cancer did not involve the skin next to the tympanic membrane, no evidence of cancer recurrence has been seen and conductive hearing has been preserved.
When the cancer involves the middle ear structures, a subtotal temporal bone resection has to be carried out. Tumors involving the inner ear structures require a total temporal bone resection. Tumors that involve the dura (brain covering) are generally not curable, as the cancer cells have likely spread throughout the cerebrospinal fluid space. Palliative resection will rarely be performed when the survival of the patient cannot be extended with surgery.
In this patient, an MRI showed the cancer had involved the parotid gland. A repeat CT scan three months after the initial scan showed the bony canal had been almost entirely destroyed and the middle ear had become involved. This cancer clearly took a very aggressive course in a short period of time, which may be due to the invasion and breach of the bony external auditory canal.
The lesson to learn from this case is that if something looks like cancer but is not found to be cancer on biopsy, a repeat biopsy with removal of a larger portion of the mass is necessary. This may require a short procedure under anesthesia, allowing the clinician to take a larger specimen for proper diagnosis. A persistent vascular mass in the ear canal should be taken seriously.
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 shows the Axial CT of the temporal bone showing extensive destruction of the external auditory canal.
- Video 2 shows the Coronal CT of the temporal bone demonstrating no invasion of the roof of the ear canal.
- Video 3 shows the Sagittal CT of the temporal bone showing the degree of funny destruction in the anterior canal wall.
- Video 4 shows the Axial T-1 post contrast MRI of the temporal bone showing enhancement of the external auditory.
- Video 5 shows the Coronal T-1 post contrast MRI of the temporal bone showing enhancement along the entirety of the cartilaginous canal.
- Video 6 shows the Axial T1 post contrast MRI of the neck showing the relationship between the ear canal and parotid gland.
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