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Q1: What is the diagnosis?
The diagnosis is adenoid cystic carcinoma (ACC) of the external auditory canal. It is commonly seen in the glandular tissues like salivary glands, breast, larynx, cervix, lacrimal glands, ear canal, etc. These tumours are slow growing but highly malignant. Microscopically four patterns are described: tubular, cribriform, basal, and solid varieties. Tubular and cribriform types have a better prognosis than basal and solid types.1
Q2: What further investigation is required?
High resolution computed tomography of the temporal bone should be done in this case. It will reveal the extent of the tumour, including the integrity of osseous structures and intracranial invasion of the tumour.
Q3: What are the peculiarities of this tumour?
ACC has a remarkable tendency for invasion of the perineural spaces, so it may present as facial nerve paralysis irrespective of the size. In view of recurrences after a long tumour-free period, unlike squamous cell carcinoma, survival rates of ACC should be assessed at 10, 15 and even 20 years, to be able to determine the ultimate prognosis of the tumour.2
Q4: What is the treatment?
Recommended treatment for ACC of ear canal is radical surgery followed by radiotherapy. These tumours are not radiosensitive but radiotherapy has been proved to act on the residual tumour and suppress local recurrences.3
Tumours of the external auditory canal and middle ear as a group are extremely uncommon. Most of these usually involve pinna. Squamous cell carcinoma is the commonest, accounting for about 80% of malignancies. ACC is the second most common tumour of the ear canal (7%).4 Histological and biological properties are similar to those of its counterparts in the salivary glands. The natural history of this tumour is characterised by a long, relentless course with a tendency for perineural invasion, local recurrence, and distant metastasis.5 The lung is the most common site of metastasis. Histologically ACC in the ear canal should be differentiated from other adenomatous tumours, namely adenoma, mixed tumour arising from cereminous glands, basal cell carcinoma, and adenocarcinoma. ACC characteristically contains tubular and cribriform structures with a single layer of cells having scanty cytoplasm.1
High resolution computed tomography is extremely important in management. It shows ossicular status, inner ear involvement, and intracranial extension.6
These tumours should be treated by radical surgery followed by radiotherapy. Long term follow up is required because there is a propensity for local recurrence and distant metastasis even up to 20 years.2
Adenoid cystic carcinoma of the external auditory canal.