[A case of malignant peripheral nerve sheath tumor of the kidney]

We report a case of malignant peripheral nerve sheath tumor (MPNST) of the kidney. A 50-year-old man was referred to our hospital because of left back pain. Computed tomographic scan and magnetic resonance imaging revealed a huge left retroperitoneal tumor (30 x 13 x 11 cm), which consisted of a solid tumor with calcification surrounding the cystic component. He underwent resection of the retroperitoneal tumor and additional descending colectomy. Histopathological examination revealed MPNST arising from severely atrophic renal parenchyma of giant hydronephrosis. He died of tumor metastasis to the lungs 3 months after the operation. To our knowledge, this is the fourth case of MPNST of the kidney, moreover the third case arising from the renal parenchyma to be reported in Japan.