Fetal rhabdomyomatous nephroblastoma: a tumour of good prognosis but resistant to chemotherapy

Fetal rhabdomyomatous nephroblastoma (FRN) is a rare variant of Wilms' tumo ur. The tumour chiefly consists of fetal striated muscle with particularly distinct striations and central nuclei. To determine the effect of (preoper ative) chemotherapy in the treatment of this subtype of nephroblastoma, a r etrospective analysis was performed. By 1 November 1991, SIOP 9 had registe red 852 patients (pts) from 55 centres. We report on 13 children diagnoses with FRN between 1988 and 1992 with a median age of 2 years and 1 month (ra nge 1 month-8 years 6 months). There were 7 boys and 6 girls. 9 patients we re classified as stage I, 2 as stage II, 1 as stage III and 1 as stage V. 1 2 patients received preoperative chemotheraphy with actinomycin-D and vincr istine for 2 weeks (1 pt), 4 weeks (5 pts) and 8 weeks (6 pbs) respectively . The average tumour volume at registration (determined by ultrasonography) in 12/13 patients was 965 cm(3) (range 17.3-2520 cm(3)). 3/7 of the FRN pa tients showed no tumour regression after 4 weeks preoperative CT and 4/8 af ter 8 weeks preoperative chemotheraphy (compared with only 28 and 34% after 4 and 8 weeks CT, of all trial patients). Of 13 patients, 10% are alive an d free of disease with a mean follow up of 4 years. This variant of Wilms' tumour is a poor responder to preoperative chemotheraphy and is associated with a generally favourable outcome in most of all unilateral cases when tr eated by surgery. (C) 1999 Elsevier Science Ltd. All rights reserved.