腎混合性上皮性間質腫瘍の1例

A case of renal mixed epithelial and stromal tumor

腎混合性上皮性間質腫瘍（腎mixed epithelial and stromal tumor：腎MEST）は，認知度の低い腎腫瘍で，画像上は嚢胞成分と間質成分をもつ境界明瞭な腫瘍として描出される。発生には女性ホルモンの関与が指摘されており，中高年の女性に多く，前立腺癌ホルモン療法後の男性に発生することもある。今回我々は，画像所見，患者背景とも腎MESTの特徴的所見に合致していた症例を経験したため，文献的考察を加えて報告する。

We report a case of a woman in her 40s with renal mixed epithelial and stromal tumor（MEST）without symptoms. CT showed a multicystic lesion at the left kidney with hyperattenuating septums. On dynamic contrast–enhansed CT, the septums were enhanced gradually. A dynamic contrast–enhansed MRI showed a multicystic lesion with septums which was low intensity on T2 weighted image. The septums were enhanced gradually. From the result of CT and MRI, a multicystic lesion was thought to be Bosniak classification category Ⅲ. Low–grade multilobular cystic renal tumor and renal MEST were suspected, and laparoscopic nephroureterectomy was performed. The pathological diagnosis was renal MEST. Renal MEST is an underrecognized renal tumor which has a cystic lesion and stromal components. Female hormones have been implicated in its development, and it is more common in middle–aged women. In this case, both imaging features and patient backgrounds were consistent with the characteristics of renal MEST.