Squamous Cell Carcinoma Recurring to the Great Auricular Nerve

Figure 1: Contrast-Enhanced Axial CT Scans, Superior to Inferior

Figure 2: Dose Distributions in the Axial (left), Coronal (middle), and Sagittal (right) Planes

The Case: A 74-year-old man presented with a 2.5-cm ulcerated mass occupying the middle third of his left outer ear, approximating the helical rim. He underwent wide local excision with placement of a full-thickness skin graft. Pathology results were positive for moderately differentiated invasive squamous cell carcinoma (SCC), with a 1-mm focus of residual SCC identified at the peripheral re-excision margin. He underwent excision of a local recurrence 3 months later, and excision of a new mass near his antitragus 3 months after that. A physical examination 4 months after excision of the new mass revealed a dense cord of thickened tissue in the expected location of the great auricular nerve. Biopsy results were positive for SCC with perineural involvement.

A CT scan of his neck revealed an enhancing mass extending from the level of the inferior parotid gland and traversing the lateral aspect of the sternocleidomastoid muscle; the enhancing mass clinically correlated with the cord-like structure palpated on physical examination (Figure 1).

The patient underwent a left modified radical neck dissection and re-excision of the left neck SCC with facial nerve monitoring. Operative findings revealed gross involvement within the great auricular nerve itself, which wrapped around the posterior edge of the sternocleidomastoid muscle. The nerve was removed along with a nearly 1-cm cuff of sternocleidomastoid muscle. Pathology results revealed a moderately differentiated SCC surrounding the nerve, with the deep soft-tissue margin approximately 0.1 cm from the tumor. Six level II–IV lymph nodes and one level V lymph node were negative for metastatic SCC.

Since the patient experienced multiple local recurrences within a relatively short period of time and with the presence of a close deep surgical margin, adjuvant external beam radiotherapy (EBRT) was recommended. CT-based treatment planning (axial images at 0.25-cm intervals from the top of the head to below the sternal notch) in the supine position with custom head and shoulder Aquaplast immobilization was performed. Intravenous contrast was delivered to allow better visualization and delineation of the neck vessels. Image-guided intensity-modulated radiotherapy was delivered once a day, Monday through Friday, utilizing a 9-field technique with 6-MV photons over 7 weeks. The planning target volume was defined as any areas of potential microscopic disease with margin (the remnant left earlobe, pre- and post-auricular areas, C2–C3 cranial nerve branches and neural foramina, upper neck, and sternocleidomastoid muscle/great auricular nerve tumor bed). The patient received 50 Gy in 2.0 Gy fractions. An additional 16 Gy in 2.0 Gy fractions was delivered to the remnant left earlobe and sternocleidomastoid muscle/great auricular nerve tumor bed for a total dose of 66 Gy in 33 fractions (Figure 2).

Nine months after the completion of treatment the patient developed dysphagia requiring dilation. In addition, he required a left ear amplifier. He is now tumor-free 26 months after surgery and adjuvant radiotherapy.

Discussion

This patient had a rare and unusual presentation of SCC of the outer ear that involved the great auricular nerve when it recurred. The great auricular nerve comprises nerve fibers arising from C2 and C3 of the cervical plexus and lies within the superficial cervical fascia overlying the sternocleidomastoid muscle.[1] This nerve consists of anterior and posterior branches providing sensory innervation to the skin overlying the parotid gland, outer ear, and mastoid process.

Perineural tumor spread is often seen in cutaneous and mucosal SCCs of the head and neck. It is thought to be caused by cancer cells invading the perineural space, which compromises the neural blood supply and results in segmental infarction of the neural bundle, leading to axon and myelin degeneration.[2] Interestingly, perineural spread was not reported in any of the patient’s initial pathologic reports prior to his great auricular nerve biopsy. The diagnosis was suspected on physical examination because of the dense cord of thickened tissue in the expected location of the great auricular nerve; a CT scan, which showed both enlargement and abnormal enhancement of this nerve, helped to confirm the diagnosis. As with any cutaneous lesion of the head and neck, the potential exists for perineural spread along the cervical plexus, as well as retrograde perineural spread into the cervical plexus itself.[3] Because of this, radiation treatment fields were expanded to encompass not only the great auricular nerve tumor bed where the margin was deemed close, but also the nerve roots and neural foramina of C2 and C3.

The patient’s clinical history and physical examination led the clinician to the diagnosis of recurrent SCC to the great auricular nerve. His history of multiple recurrences, subsequent operative findings, and tumor pathology substantiated the need for adjuvant EBRT. Successful treatment required attention to the patient’s physical findings, an understanding of the anatomy of the cervical plexus, and knowledge of the potential for retrograde perineural tumor spread.

Financial Disclosure:The authors have no significant financial interest or other relationship with the manufacturers of any products or providers of any service mentioned in this article.

E. David Crawford, MD, serves as Series Editor for Clinical Quandaries. Dr. Crawford is Professor of Surgery, Urology, and Radiation Oncology, and Head of the Section of Urologic Oncology at the University of Colorado School of Medicine; Chairman of the Prostate Conditions Education Council; and a member of ONCOLOGY’s Editorial Board. If you have a case that you feel has particular educational value, illustrating important points in diagnosis or treatment, you may send the concept to Dr. Crawford at david.crawford@ucdenver.edu for consideration for a future installment of Clinical Quandaries.

References:

1. Berry M, Bannister LH, Standring SM. Nervous system. In: Williams PL, Bannister LH, Berry MM, et al, editors. Gray’s Anatomy. 38th ed. New York: Churchill Livingstone; 1995. p. 901-1397.

2. Carter RL, Foster CS, Dinsdale EA, Pittam MR. Perineural spread by squamous carcinomas of the head and neck: a morphological study using antiaxonal and antimyelin monoclonal antibodies. J Clin Pathol. 1983;36:269-75.

3. Ginsberg LE, Eicher SA. Great auricular nerve: anatomy and imaging in a case of perineural tumor spread. AJNR Am J Neuroradiol. 2000;21:568-71.