Case of the Week
Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
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February 28, 2019
Perineural spread of squamous cell carcinoma to the greater auricular nerve
- Background
- Perineural tumor spread is the process by which cancer cells surround a nerve sheath and spread along the length of a nerve.
- Perineural tumor spread is most commonly seen in cutaneous squamous cell carcinomas, although it can be seen in other tumors such as adenoid cystic carcinoma.
- It most commonly involves the trigeminal and facial nerves, with spread involving the greater auricular nerve and the cervical plexus rarely seen.
- The greater auricular nerve (GAN) is a superficial branch of the cervical plexus (with C2 and C3 spinal nerve contributions) that provides cutaneous innervation to the areas overlying the parotid gland, the external ear and the posterior auricular region. Given the nerve’s anatomical origins, it is important that imaging cover down to the level of C5 in those patients with cutaneous peri-auricular symptoms.
- Clinical Presentation
- Perineural tumor spread usually presents with a slowly progressive neuropathy with pain, anesthesia, or other dysesthesias such as a tingling sensation in the distribution of the nerve involved, often with a history of previous skin cancer excision.
- Key Diagnostic Features
- Abnormal enhancement or thickening of the nerve.
- Obliteration of the normal fat plane surrounding the nerve.
- Erosion or enlargement of neural foramen.
- MRI is the preferred method for assessing the nerves, while CT may be helpful in assessing bony involvement in advanced stages.
- Differential Diagnosis
- Generally an unambiguous diagnosis.
- Abnormal neural enhancement may also be seen in viral neuronitis, IgG disease, fungal infections, lymphoma and sarcoidosis.
- Treatment
- Complete surgical resection is the main treatment, generally followed by adjuvant radiotherapy.
- Pre-operative planning with targeted MRI is essential to determine the extent of disease spread and maximise the chance of complete resection with clear margins.
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