Ploidy changes between diagnosis and relapse in childhood renal tumours

Ploidy patterns, analysed by flow cytometry (FCM) and image analysis (IA), were investigated at relapse in a group of six children with renal tumours [five Wilms' tumour (WT) and one bone metastasizing renal tumour of childhood (BMRTC)] and results compared with diagnostic profiles. IA detected one or more aneuploid populations in five of 12 tumours which were diploid on FCM. Patterns in three of six patients [two with unfavourable histology (UH) and one with favourable histology (FH)] were aneuploid at diagnosis and relapse, two patients (one FH, one BMRTC) developed aneuploid features at relapse and one patient with a tetraploid tumour was diploid at relapse. Histology patterns were similar at diagnosis and relapse in all patients. Three of six patients (two UH, one BMRTC) have died of disease. This report highlights (1) the superiority of IA over FCM in detecting aneuploid populations and (2) changes in ploidy status which have not previously been reported in these tumours. Overinterpretation of DNA status at relapse may prove misleading.