Malignant Neoplasms of the Ear and Temporal Bone

Clinical Features

SCCs of the external auditory canal (EAC) are uncommon (1/million population), quite different from pinna SCC. Patients are usually older (mean, 55 to 65 years), but women are affected more often than men for EAC carcinomas, opposite of pinna carcinomas. A serious problem with EAC and middle ear tumors is the delay in diagnosis because of the nonspecific symptoms that may be present ( Fig. 19.1 ), different from much earlier detection of pinna lesions due to their prominent position. Chronic otitis media and radiation exposure are etiologies considered, quite different from ultraviolet exposure or frostbite for pinna tumors. Transformation of squamous papilloma is rare. Patients present with a mass, otitis media, otitis externa, pain, hearing loss, discharge, and/or bleeding. In the later stages, there may be dissolution of the tympanic membrane with invasion into the middle ear, bone, and internal auditory meatus. Tumor may also enter the middle ear by posterior canal entry into the mastoid air spaces ( Fig. 19.2 ). Isolated cases (usually younger patients) may show middle ear confined tumors. Interestingly, concomitant cholesteatoma is usually not found.

Pathologic Features

Microscopic Findings

SCC of the EAC and middle ear is similar to other sites, separated into well, moderately, and poorly differentiated; keratinizing and nonkeratinizing; and in situ versus invasive ( Fig. 19.2 ). There are nests, sheets, and infiltrative cords, keratin pearl formation, atypical keratinization, polarity loss, intercellular bridges, opacified cytoplasm, nuclear chromatin condensation, and increased mitotic figures, including atypical forms ( Fig. 19.3 ). Perineural invasion is associated with a high rate of local recurrence and increased risk of metastasis. Middle ear tumors may show chronic inflammation and often marked desmoplastic stroma. In cases arising deeply within the ear canal, there is often dissolution of the tympanic membrane and a concomitant origin from the middle ear epidermis (squamous metaplasia arising from the simple cuboidal epithelium), although passage into the middle ear is possible without damage to the eardrum ( Fig. 19.4 ). An origin directly from middle ear epithelium may also be seen. Other variants include verrucous, spindle cell, and adenoid squamous cell carcinoma. High-risk patterns include spindle cell/sarcomatoid ( Fig. 19.5 ), basaloid, adenosquamous, and desmoplastic SCCs.

Although cholesteatoma may be concurrently identified with SCC, SCC does not develop from cholesteatoma. Spread of SCC within the middle ear is extremely rare due to the peculiar resistance of the bone of the otic capsule to direct spread of the tumor. Nonetheless, this spread begins with early erosion through the thin bony plate (up to 1 mm thick) that separates the medial wall of the middle ear at its junction with the eustachian tube from the carotid canal. Further extension along the carotid canal eventually allows for easy extension to the sympathetic nerves, making the tumor impossible to eradicate surgically. In addition, tumor spreads through the bony walls of the posterior mastoid air cells to the dura of the posterior surface of the temporal bone.

Ancillary Studies

Immunostains are used primarily for poorly differentiated and spindle cell tumors. High-molecular-weight (HMW) cytokeratins 5/6 and CK903 (34βE12) are the most sensitive markers for squamous differentiation and, along with p63 or p40, help to confirm the diagnosis in these more difficult cases.

Differential Diagnosis

Middle ear corpuscles, concentrically laminated balls of collagen formed on bone-free mastoid air cell partitions, are more common in the elderly and may be difficult to separate from SCC, particularly in frozen sections. However, there is an absence of cells in the laminated corpuscles. Cholesteatoma does not show pleomorphism, desmoplastic stroma, or atypical mitoses. Otic polyp shows chronic inflammation without well-developed epithelial atypia or atypical mitoses.

Prognosis and Therapy

Squamous carcinoma of the external canal and middle ear is an aggressive disease with a high propensity for local recurrence. Poor prognostic features include high clinical stage, > 8 mm tumor depth, perineural, and/or lymphovascular invasion. Death is usually due to direct intracranial extension. Lymph node metastasis is unusual (< 10%) and hematogenous spread even more rare. Optimal therapy is complete surgical excision, with radiation therapy.

If the middle ear is involved, the neoplasm is surgically incurable if either or both (1) the thin plate of bone between the internal carotid artery and the tympanic end of the eustachian tube and (2) the bone in the posterior wall of the mastoid, bordering the posterior cranial fossa, are breached by tumor. In the absence of these features middle ear squamous carcinoma is often treated by “petrousectomy,” which is by no means a resection of the whole petrous bone but a subtotal resection or extirpation of the middle ear components involved by tumor.