Chapter 3 Malignancies of the Temporal Bone—Limited Temporal Bone Resection

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Although carcinoma of the temporal bone is uncommon and aggressive, the best outcome depends on careful evaluation and planning that result in a complete resection with pathologically clear surgical margins. The most common lesion is primary squamous cell carcinoma of the external auditory canal (EAC); however, direct extension by pinna and salivary gland lesions, metastatic lesions, and adenocarcinomas of the glandular adnexa of the ear canal and pinna are potential lesions. Tumors involve the temporal bone through primary growth, direct extension, and metastatic spread. The consequences of these lesions include morbidity owing to anatomic remodeling, intracranial extension, perineural spread, vascular encasement and dural invasion, and ultimately death.

Historically, carcinoma of the temporal bone was an ominous diagnosis. Advancements in diagnostic and surgical technique have led to greatly improved outcomes. The successful resection of T1 disease has shown survival outcomes of 95%, and the treatment of T2 and T3 disease has shown survivals of 85% when a clear surgical margin is combined with postoperative radiation therapy.¹

A multidisciplinary approach to the diagnosis and treatment of these lesions offers the best possible outcome. Surgery and postoperative radiation represent the principal treatment arms; however, interest in a possible combined role for chemotherapy is increasing.² The type of resection needed is determined by the extent of disease. A sound oncologic resection can be achieved through a lateral temporal bone resection, subtotal temporal bone resection, or total temporal bone resection with such additional simultaneous procedures as parotidectomy, facial nerve resection, mandibulectomy, and cervical lymphadenectomy as indicated. When the surgery has been planned, reconstructive options should be explored. Great strides have been made over the past century in the surgical and nonsurgical management of temporal bone neoplasms, but they remain a significant treatment challenge.

TUMOR CONSIDERATIONS

The incidence of tumors of the temporal bone is 200 new cases per year with a frequency of 6 cases per 1 million. Squamous cell carcinoma accounts for 86% of these tumors. Possible etiologic factors include industrial exposure to petroleum-based products, topical disinfectants, and chronic infection. Basal cell carcinoma, adenoid cystic carcinoma, adenocarcinoma, and ceruminous carcinoma occur less frequently.³^–⁵ Tumors of mesenchymal origin are as rare, with rhabdomyosarcoma occurring most frequently.⁶ Salivary gland tumors can originate from ectopic rests of salivary tissue within the middle ear (pleomorphic adenoma has been described in that location), or from minor salivary glands within the EAC, but both are rare.⁷

Salivary gland tumors are more likely to involve the temporal bone through direct extension from the parotid gland. The anatomic relationship between the temporal bone and parotid gland is responsible for this tendency. The parotid gland is located in close proximity to the mastoid and tympanic portions of the temporal bone. It communicates directly with the cartilaginous EAC through the fissures of Santorini and foramen of Huschke.⁸ The stylomastoid foramen, carotid canal, jugular foramen, petrotympanic fissure, and eustachian tube provide avenues for intratemporal extension. In primary temporal bone carcinoma, these anatomic pathways are particularly significant as routes for extension beyond the temporal bone to the adjacent parotid tissue and soft tissue at the base of the skull base.

In rare cases of temporal bone involvement by benign tumors of the parotid gland, symptoms of a facial mass, trismus, or compression of the parapharyngeal space by tumor usually precede temporal bone involvement.⁹ Additionally, benign masses have a tendency to compress or remodel adjacent tissue, rather than invade it. This tendency allows for extirpation of a benign parotid neoplasm, in some cases, without requiring a formal temporal bone resection. These lesions can be removed through traditional parotidectomy techniques. Disarticulation of the mandibular condyle, resection of the EAC, or mastoidectomy may be necessary to assist with resection. Pleomorphic adenoma of the tail of the parotid gland can manifest as a subcutaneous mass of the floor of the lateral portion of the EAC. This situation is best managed with combined superficial parotidectomy with mastoidectomy and postauricular canalplasty.

Temporal bone involvement by malignancies of salivary gland origin is aggressive and involves adjacent tissue more readily. Tumors can develop insidiously and relatively asymptomatically, with 75% manifesting with a painless mass and only 6% to 13% manifesting with facial nerve palsy. Symptoms may not be present until after temporal bone invasion has occurred. Pain, dysphagia, and dysphonia can occur after direct invasion of the skull or involvement of the lower cranial nerves at the jugular foramen. Direct extension into bone, fissures, and foramina are potential routes of spread. Mass lesions of the poststyloid parapharyngeal space can traverse the carotid canal and jugular foramen, and neurotrophic tumors, such as adenoid cystic carcinoma, follow the facial nerve as an avenue toward the stylomastoid foramen. Carcinoma of the auricle, anterior scalp, or face that has spread to the intraparotid lymphatics can involve the temporal bone in a similar fashion. In a review of 27 cases of advanced and recurrent parotid neoplasms requiring temporal bone resection, Leonetti and colleagues ⁹ found that adenocarcinoma occurred most commonly followed by adenoid cystic carcinoma and mucoepidermoid carcinoma.

Malignancies involving the temporal bone present a formidable problem. Without treatment, these lesions result in a high incidence of morbidity and almost certain death. Extension into the otic capsule and petrous bone can result in hearing loss, vestibulopathy, cranial neuropathies, and hemorrhage. Malignant spread into the middle and posterior fossa and extension into the petroclival region or cavernous sinus portend a grim prognosis even with aggressive surgical efforts. In cases of distant metastatic disease, a temporal bone resection may still be indicated for palliation.