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Cancer of the Auditory Canal

Uncommon cancer generally best treated with combined surgery and radiation (see discussion below from Perez textbook and other recent studies from the literature.)
The external ear consists of the auricle or pinna, the external auditory meatus (canal), and the tympanic membrane (see anatomy). The auricle is composed of elastic cartilage covered with skin. The external auditory meatus connects the tympanic membrane to the exterior and is approximately 2.4 cm long. The outer third is cartilaginous, and the inner two thirds is bony and slightly narrower.The external auditory canal is related anteriorly to the parotid gland at the temporomandibular joint. Inferiorly, it lies near the jugular bulb and the facial nerve as it descends through the stylomastoid foramen.

ear_canal_data.gif (18305 bytes) The skin lining the auditory canal is continuous with that of the auricle, and in the outer third of the canal, it contains hair follicles and sebaceous and ceruminous glands. Lymphatic vessels of the tragus and anterior external portion of the auricle drain into the superficial parotid lymph nodes. Those of the posterior external and whole cranial aspect of the auricle drain into the retroauricular lymph nodes, and those of the lobule drain in the superficial cervical group of lymph nodes. Lymphatics from the middle ear and the mastoid antrum pass into the parotid nodes and into theupper deep cervical lymph nodes. The lymphatics in the middle ear and eustachian tube are rather sparse, and the inner ear has no lymphatics.
 
External Auditory Canal Cancer

Most patients present with symptomatic lesions of the external canal. Pruritus and pain are common. Swelling behind the ear, decreased hearing, and facial paralysis are seen in advanced cases. Spread of the tumor into the lymphatic areas is more common than to other areas
of the ear. Tumors arising in the cartilaginous portion of the canal invade the cartilaginous walls and spread into the bony canal areas. However, those arising in the bony canal have a more effective barrier (preventing spread) and therefore progress predominantly along the main axis of the canal, eventually invading the middle ear or the cartilaginous part of the canal. Distant metastases are rarely seen with these tumors.About 85% of the tumors involving the auditory canal, middle ear, and mastoid area are squamous cell carcinomas. Infrequently, basal cell carcinomas, adenocarcinomas, adenoid cystic carcinomas, and melanomas are seen.

Radical surgery and postoperative radiation therapy are the accepted methods of treatment for more advanced lesions of the external auditory canal and lesions in the middle ear and mastoid. Except in tumors that are detected early, neither modality is considered optimal, and a combination of the two produces the best results.Lesions of the outer part of the auditory canal require local excision with at least a 1-cm margin between the lesion and the tympanic membrane if there is no radiographic evidence of invasion of the mastoid. Surgery for tumors of the auditory canal is performed through a U-shaped incision with elevation of the flap from below. A split-thickness skin graft is usually required to cover the deficit along the auditory canal.

When the tumor involves the bony auditory canal and impinges on the tympanic membrane but does not involve the middle ear or the mastoid, a partial temporal bone resection may be necessary; in this procedure the auditory canal, tympanic membrane, malleus, and incus are removed
along with the temporomandibular joint, and the defect is grafted with a split-thickness skin graft. Large lesions of the external auditory canal are treated with irradiation alone or combined with surgery; the portals should encompass the entire ear and temporal bone with an adequate margin (3cm). The volume treated should include the ipsilateral preauricular, postauricular, and subdigastric lymph nodes. Treating lymphatics
beyond the jugulodigastric area is usually not necessary.

Extremely advanced tumors that are unresectable should be treated with high-energy ipsilateral electron-beam therapy (16 to 20 MeV) alone or mixed with photons (4 to 6 MV) or with wedge pair (superior inferiorly angled beams) techniques using low-energy photons. Doses of 60 to 70 Gy over 6 to 7 weeks are required.