RESUMEN
INTRODUCTION: Majority of Wilms tumour (WT) responds well to pre-operative chemotherapy. In Malaysia, incidence of WT is rare with only two cases reported per one million populations yearly. This case report is to highlight on the awareness of WT in an Asian population and highlight two cases and challenges faced after pre-operative chemotherapy. CASE REPORT: In this case series, we report on two cases of WT which had poor response to pre-operative chemotherapy. Both cases underwent surgery after pre-operative chemotherapy and recovery was uneventful during a two-year follow-up. DISCUSSION: Both patients had chemotherapy prior planned surgery, but had unfortunate poor tumour response. The tumour progressed in size which required a radical nephrectomy. The histology report for the first case had more than 60% blastemal cells remaining despite giving pre-operative chemotherapy with no focal anaplasia. This showed poor response to chemotherapy evidenced by the high number of blastemal cells. The second case was a stromal type WT which is known for poor response and may lead to enhancement of growth and maturation induced by chemotherapy. These were the possible reason of poor response of WT in these two cases.