[A case of primitive neuroectodermal tumor of the kidney]

A primitive neuroectodermal tumor (PNET) is a solid tumor originating from the neural crest. This tumor is known to occur in the central nervous system and soft tissue, but recently determined to also invade the kidney. Although primary renal PNET is very rare, we encountered a case of primary renal PNET with multiple lung metastasis. This case was a 35-year-old man with a chief complaint of macroscopic hematuria, which he noticed in January 1996. He was hospitalized because of right renal tumor detected with ultrasonography. On CT scan, a low-density solid tumor with a maximum diameter of 8 cm was visualized in the right kidney. Low-signal and high-signal tumorous lesions were demonstrated in the same region on T 1-weighted and T 2-weighted MR images, respectively. Then right radical nephrectomy was performed on Feb. 5, 1996. On histopathological observation, the tumor was composed of small tumor cells with solid growth. Immunohistochemical staining revealed that the tumor was positive for CD 99. Thus our final diagnosis was primary right renal PNET. Although 2 metastatic lesions with a diameter of about 1 cm were observed in the right lower lung before the time of surgery, pulmonary metastatic lesions markedly increased in number 3 months after surgery. Thus we initiated CAP chemotherapy with cyclophosphamide, doxorubicin, and CDDP. After 3 cycles, pulmonary metastatic lesions disappeared at CT scan, indicating complete remission. However, a tumor with a maximum diameter of about 10 cm recurred in the retroperitoneum 7 months after complete remission. Although 2 cycles of CAV/PE therapy with cyclophosphamide, doxorubicin, vincristine, CDDP, and VP-16 were performed following resection of the retroperitoneal tumor, he showed no response and decreased 24 months after surgery.