Anaplastic histology Wilms' tumors registered to the Japan Wilms' Tumor Study Group are less aggressive than that in the National Wilms' Tumor Study 5

To evaluate the clinical features and treatment results of anaplastic histology (AH) Wilms' tumor (WT) patients registered in the Japan Wilms' Tumor Study (JWiTS) group to elucidate the clinical characteristics of AH in the Japanese population.

Of 344 WT patients who were enrolled in JWiTS between 1995 and 2013, 17 had AH. Treatment using the JWiTS protocols was similar to the fifth National Wilms' Tumor Study 5 (NWTS-5) protocols. Clinical characteristics and mutation status of TP53 gene were evaluated and compared with those in NWST-5 study.

AH incidences in JWiTS were 4.9 %, lower than that in NWTS-5. Seven tumors had focal AH and 10 had diffuse AH. Clinical stages of AH patients were stage I in seven, stage II in three, stage III in five, stage IV in one and unknown in one. Four-year event-free survival and overall survival rates were 90.9 and 86.7 %, respectively. Two patients with diffuse AH and none with focal AH had TP53 mutation.

Japanese patients presented with higher incidence, earlier stages and may have better outcomes than American patients, indicating a possible biological heterogeneity of AH WT. Further analysis is necessary to elucidate the different characteristic of AH WT between Japanese and American populations.

Pediatric surgery international. 2016 Jul 29 [Epub ahead of print]

Takaharu Oue, Tsugumichi Koshinaga, Tetsuya Takimoto, Hajime Okita, Yukichi Tanaka, Miwako Nozaki, Masayuki Haruta, Yasuhiko Kaneko, Masahiro Fukuzawa, Renal Tumor Committee of the Japanese Children’s Cancer Group

Department of Pediatric Surgery, Hyogo College of Medicine, 1-1 Mukogawa-cho, Nishinomiya, Hyogo, 63-8501, Japan. ., Department of Pediatric Surgery, Nihon University School of Medicine, Itabashi-ku, Tokyo, Japan., Division of Registration and Research for Childhood Cancer, National Center for Child Health and Development, Setagaya-ku, Tokyo, Japan., Department of Pathology, Keio University, Shinjyuku-ku, Tokyo, Japan., Department of Pathology, Kanagawa Children's Medical Center, Yokohama, Kanagawa, Japan., Department of Radiology, Dokkyo Medical University Koshigaya Hospital, Koshigaya, Saitama, Japan., Research Institute for Clinical Oncology, Saitama Cancer Center, Ina, Saitama, Japan., Research Institute for Clinical Oncology, Saitama Cancer Center, Ina, Saitama, Japan., Osaka Medical Center and Research Institute for Maternal and Child Health, Izumi, Osaka, Japan.