44歳男.右陰嚢の無痛性腫大を主訴に受診, エコー, CT, MRIで右精巣腫瘍と診断され, 右精巣摘除術を施行した.病理結果は陰嚢類表皮嚢胞であった.精巣の良性腫瘍として類表皮嚢胞は多くの報告があるが, 陰嚢内に発生し, 精巣や精索に無関係なものは極めて稀である.陰嚢類表皮嚢胞は陰嚢の良性腫瘍であり, 術前診断或いは術中迅速凍結標本において診断できれば, 精巣摘除を施行せずに済む症例であったA 44-year-old male was admitted with the chief complaint of a huge mass in the right scrotum. Computed tomography (CT), magnetic resonance imaging (MRI) and ultrasonography demonstrated a homogeneous lesion in the right testis. Under the diagnosis of right testicular tumor, surgical resection was performed and the right testis itself was found to be essentially normal. The mass contained 500 ml of liquid. The pathologic diagnosis was an epidermoid cyst of the scrotum, a rare disease with only 11 cases reported in Japan
