Carcinoma of the temporal bone is rare, accounting for fewer than 0.2% of all tumors of the head and neck. Only 200 new cases of temporal bone cancer may be diagnosed each year across the United States. This number includes cancers arising from skin of the pinna that spread to the temporal bone; primary tumors of the external auditory canal (EAC), middle ear, mastoid, or petrous apex; and metastatic lesions to the temporal bone.
Malignancies of the temporal bone arise most commonly from the pinna and lateral concha because these sites are likely to have undergone many years of sun exposure. In these areas, basal cell carcinoma and squamous cell carcinoma are most common. If neglected, these tumors may spread medially to the EAC. The most common type of primary cancer in the EAC is squamous cell carcinoma, and squamous cell carcinoma of the temporal bone may originate from the EAC or middle ear where chronic otorrhea and inflammation, cholesteatoma, or both may be associated risk factors.
Adenocarcinoma, melanoma, rhabdomyosarcoma, osteosarcoma, lymphoma, adenoid cystic carcinoma, and acinic cell carcinoma are other types of malignancies that may arise in the temporal bone. In children, rhabdomyosarcoma is the most common malignancy of the temporal bone. About 10% of all rhabdomyosarcomas occur in the ear. Tumors, such as meningioma, chordoma, parotid malignancy, and nasopharyngeal carcinoma, may spread to the temporal bone from contiguous sites. The temporal bone may also be a site for metastasis from lymphoma or malignant tumors of the breast, lung, kidney, or prostate.
Since temporal bone cancer is so rare, measuring specific etiologic factors for cancers in this area is very difficult. However, fair-skinned whites are more prone to nonmelanomatous skin cancers in other areas, especially areas exposed to ultraviolet radiation. A genetic predisposition to skin cancer may also exist, manifested as the development of skin cancers in sites not exposed to sunlight as well as sun-exposed areas. Chronic otitis media and cholesteatoma are common in patients with temporal bone cancers and have been implicated as etiologic factors (Morton, 1984; Moffat, 2005). Chronic suppurative otitis media and the resulting chronic inflammation may lead to squamous metaplasia. Human papillomavirus has been implicated in squamous cell carcinomas of the middle ear (Jin, 1997). Lim et al (2000) reported a series of temporal bone cancers in 7 patients who had undergone radiotherapy for nasopharyngeal carcinoma. These patients had a particularly poor outcome.
The complex anatomy of the temporal bone makes tumor spread difficult to predict. Tumors of the skin around the auricle may extend along the soft tissues of the neck and ear. The soft tissues are a poor barrier against tumor spread, and eventually the tumors may extend along the conchal bowl and into the EAC. The cartilage of the EAC provides minimal resistance to tumor spread. The fissures of Santorini, foramen of Huschke, and bony-cartilaginous junctions are a source of direct access to the periparotid tissues and temporomandibular joint.
Cancer in the external auditory meatus can invade posteriorly through the soft tissue into the retroauricular sulcus over the mastoid cortex. The bony canal is more resistant to cancer extension; however, erosion through the posterior bony canal provides access to the mastoid cavity. Tumor growth medially along the EAC can extend through the tympanic membrane and bony tympanic ring, allowing invasion into the middle ear. Once a tumor enters the middle ear, the hard bone of the otic capsule provides a more effective barrier against tumor spread.
In the middle ear or mastoid, tumors spread easily via the eustachian tube, round and oval windows, neurovascular structures, and extensive air spaces of the mastoid cavity. The eustachian tube and neurovascular structures of the middle ear are potential means of tumor spread beyond the temporal bone to the infratemporal fossa, nasopharynx, or neck. Aggressive tumors can erode through the tegmen tympani or mastoid into the middle or posterior fossa. The sigmoid sinus may become involved. The dura, although somewhat resistant to invasion, portends a grave prognosis if involved. The facial nerve and the stylomastoid foramen are metastatic routes to the soft tissues of the neck and the parotid. Proximal extension along the facial nerve leads toward the inner ear and posterior fossa. Leonetti et al (1996) offer an excellent review of the invasion patterns of temporal bone cancer.
Nodal metastasis is uncommon in early disease but may occur in 10-20% of cases of advanced disease (Moody, 2000; Moffat, 2005). The lymphatic drainage of the auricle and EAC extends anteriorly to the periparotid lymph nodes and parotid gland (Choi, 2003). Drainage may also occur to the jugular chain or nodes overlying the mastoid. Lymphatic drainage of the medial EAC and middle ear is to the retropharyngeal nodes or deep jugular nodes. The lymphatic drainage of the inner ear is unknown.
Distant metastasis is rare.
Patients with cancer of the temporal bone most often present when aged 60 years or older, although any age group, including children, can be affected. Common presenting symptoms include chronic otalgia, otorrhea, bleeding, and hearing loss. Physical findings include otorrhea, a mass lesion, facial swelling, facial paresis, and other cranial nerve (CN) deficits. Patients often present after many years of symptoms. In a series from the authors’ institution, the average time from the onset of symptoms to the time of primary treatment for cancer was 3.9 years (Moody, 2000). Nodal disease is present in 10-20% of patients (Moody, 2000; Moffat, 2005).
Physical examination should include inspection of the pinna, EAC, and middle ear for ulcers, mass lesions, soft tissue swelling or induration, old scars (eg, previously excised skin cancers may have been forgotten by the patient), and otorrhea. Perform a thorough CN examination. Close inspection for facial weakness is crucial. Perform audiography if hearing loss is suspected. As always, perform a complete head and neck examination. The patient’s general medical condition should also be evaluated because it may greatly impact treatment options and outcome.