LAUSR

BACKGROUND Generally, asymptomatic epidermoid cysts (ECs) or those with minor symptoms controlled by medication are not treated further. Although epidermoid carcinomas are sporadically reported, the possibility of their malignant transformation is of concern. CASE DESCRIPTION A 77-year-old man under observation for his left cerebellopontine angle (CPA) tumor presented with no symptoms, including headache, dizziness, or other cranial nerve abnormalities typical of CPA angle tumors. The tumor presented as an extra-axial mass in the left CPA and measured 24 x 16 mm (length x width) on magnetic resonance imaging (MRI). Since he was asymptomatic, his primary physician did not pursue invasive treatment but followed-up with an MRI every two years. Interestingly, the tumor reduced in size two years after the initial MRI, and there was no tumor fragmentation was observed on the patient's spinal MRI. Ultimately, the tumor shrunk to 19 x 11 mm over 22 years. CONCLUSIONS The reduction of EC is extremely rare. We report a case of spontaneous regression of EC in a male adult considering similar previous cases.