109 Temporal Bone Cancer
Cancer of the external auditory canal and middle ear is rare. Severe otalgia, bloody otorrhoea and visible irregularity are suspicious clinical features. The mainstay of treatment is surgery, usually with post-operative radiotherapy. The minimal operation is a lateral temporal bone resection. The morbidity of surgery with very advanced cancers is high and the chance of cure is generally poor.
109.1 Epidemiology and Pathology
Primary cancers of the temporal bone are comparatively rare, with an incidence of less than 1 per million per year. Mostly, they are squamous cell carcinomas (SCCs) arising in the external auditory meatus (EAM). Middle ear SCC is even less common. The only aetiological factor relevant in some cases is chronic inflammation, in the form of otitis externa or suppurative otitis media, or an unstable, chronically infected post-surgical mastoid cavity.
These cancers arise from the epithelial surface and spread along that surface and deeply into the underlying bone. Further local spread depends on the anatomical location of the primary cancer, but can extend superiorly through the tegmen into the middle cranial fossa; anteriorly into the temporomandibular joint (TMJ) or parotid gland; posteriorly into the mastoid air cells; or medially into the middle ear and labyrinth. The facial nerve can be involved medially and posteriorly. Extensive spread along the lateral skull base can involve other cranial nerves (IX, X and XII). Lymph node metastasis can be to intraparotid lymph nodes, and/or to cervical lymph nodes (most commonly to level 2).
Other tumour types include basal cell carcinoma (generally conchal bowl/lateral EAM), skin adnexal cancers and melanoma. Parotid cancers can invade into the temporal bone and EAM and can be confused with a primary temporal bone cancer. Any age group can be affected, although the incidence generally increases with age.
109.2 Clinical Features
While rare, cancer should be considered in any patients with more than one of chronic otalgia, bloody otorrhoea, bleeding, mass in the ear (often granulation tissue/ulceration), facial swelling or facial palsy. Some patients may have a long history of chronic middle or external ear infection. The diagnosis should also be considered in any patient with chronic suppurative otitis media (CSOM) or a mastoid cavity who develops increasing pain. Late diagnosis of patients with cancers of the EAM and middle ear (ME) is not uncommon. Different pathologies can present in a similar way. These include pseudotumoural skull base osteomyelitis of the temporal bone (also called necrotising or malignant otitis externa), and inflammatory diseases such as granulomatosis with polyangiitis.
Diagnosis is achieved by biopsy of the EAM or ME, achievable in many cases in clinic. In some cases, examination and biopsy under anaesthesia may be required.
Both computed tomography (CT) and magnetic resonance imaging (MRI) are required (temporal bone and neck). CT (fine cut, high resolution) is essential for assessing EAM erosion, extent of middle ear and mastoid involvement, spread into jugular bulb, carotid canal, tegmen, TMJ, parotid and beyond. MR differentiates mucosal swelling or mastoid fluid from tumour, is superior at ascertaining dural or brain involvement and gives more detail of parapharyngeal space and infratemporal fossa involvement. Both can also stage the neck. In addition, a CT of thorax should be done to exclude distant metastasis, as with other head and neck cancers.
A pure-tone audiogram should be performed. It informs the patient and clinicians about the level of hearing and will help to inform its subsequent management.
There is no Union for International Cancer Control (UICC) or American Joint Committee on Cancer (AJCC) staging system for cancers of the temporal bone or lateral skull base. However, many use the revised Pittsburgh staging system (Table 109.1). Standard UICC staging is used for neck and distant metastases.
Tumour limited to the EAC without bony erosion or evidence of soft tissue extension.
Tumour with limited EAC erosion (not full thickness) or radiological findings consistent with limited
Tumour eroding the osseous EAC (full thickness) with limited (< 0.5 cm) soft tissue involvement of middle ear and/or mastoid, or causing facial paralysis at presentation.