Malignant squamous degeneration of a cerebellopontine angle epidermoid tumor. Case report and review of the literature

A 57-year-old woman initially presented in July 1996 with left V3 trigeminal neuralgia, progressive hearing loss, and facial weakness. A MRI scan revealed a non-enhancing mass in the left cerebellopontine (CP) angle. An epidermoid was near-totally resected via a suboccipital craniotomy. One year later, she developed vertigo, near syncope, increased swallowing difficulty. Follow-up MRI scans in April and July 1997 revealed an enlarging, inhomogeneously enhancing mass in the left CP angle, pons, and middle cerebellar peduncle. The previous suboccipital craniotomy was reopened and a posterior petrosectomy was performed. A subtotal resection was again performed and the pathology was consistent with squamous cell carcinoma arising in an epidermoid. She subsequently received external beam radiotherapy with radiosurgery boost with good short-term response. The pathogenesis, differential diagnosis, management, and review of the literature for this rare occurrence will be discussed.