Intracranial epidermoid cysts, also known as epidermal cysts, grow slowly and may be occult. When small, epidermoid cysts are usually clinically unremarkable or cause no definitive symptoms. At typical sites, they are easily found through magnetic resonance imaging, which aids evaluation before surgery. However, in rare cases, epidermoid cysts are situated in unusual locations or transformed to malignancy, and preoperative misdiagnosis is possible. Here, the case of a 58-year-old male patient who presented with weakness in the left lower limb and was diagnosed with a malignant epidermoid cyst in the right frontoparietal lobe, right lateral ventricle, is reported. Surgery was performed to remove the tumour followed by radiotherapy, and the patient was reported to be living independently after approximately 11 months of follow-up.
Keywords: Epidermis cyst; atypical site; malignant transformation; prognosis; radiotherapy; squamous cell carcinoma.