Malignant transformation of a residual cerebellopontine angle epidermoid cyst.

Malignant transformation is a rare but devastating complication following partial resection of an intracranial epidermoid cyst (EC). Time to malignant transformation is highly variable and optimal management is unclear. A literature search from 1965 to January 2016 identified manuscripts discussing clinical presentation, management, and outcome of malignant transformation of a remnant intracranial EC. One male patient diagnosed with malignant transformation of a remnant intracranial EC in our institution was also included in the study. There were 21 patients with malignant transformation of a remnant intracranial EC, including the current patient. Mean age was 51.4years (range 36 to 77) and there was a female predominance (12 women, 9 men, ratio 1.33:1). The mean time interval from partial resection of a benign intracranial EC to malignant transformation was 7.74years (range from 3months to 33years). Surgical resection of the tumor alone was the treatment of choice in 10 patients with one of them requiring a second operation and radiotherapy 2months following the first operation. Adjuvant treatment modalities were employed in 11 patients and included radiotherapy (n=4), stereotactic radiosurgery (SRS) (n=3), chemotherapy (n=1), chemotherapy combined with SRS (n=1) and with radiotherapy (n=1) and radiotherapy combined with SRS and followed by a second tumor resection (n=1). Follow-up period ranged from 1 day to 5years and 11/19 patients (57.8%) were reported dead on follow-up. Prospective studies are required to define the optimal management of malignant transformation of remnant intracranial EC.