Neurilemmoma originating from the kidney: A case report

An eighty-two-year-old woman visited our hospital with asymptomatic macrohematuria. Ultrasonogram showed remarkable enlargement of the right kidney with irregular anechoic areas within it. CT findings of the tumor showed cystic change with internal bleeding and slight enhancement by the contrast medium. T2-weighted MR images showed heterogeneously high-signal intensity in the solid area as well as in the cystic area. Since renal cell carcinoma could not be discounted, radical nephrectomy was performed. Histological examination revealed Antoni A and Antoni B type neurilemmoma with cystic degeneration. Neurilemmoma or schwannoma is a tumor arising from the sheath of the peripheral nerves. Favored sites are cranial and spinal nerve roots, and the soft tissues of the extremities. Involvement of retroperitoneal parenchymal organs is extremely rare. This is the eighth case of primary renal neurilemmoma to be reported in Japan.