OBJECTIVE The use of a non-toxic tyrosine kinase receptor inhibitor, Imatinib Mesylate (IM), has become an ever-more common therapeutic alternative in some Kit (CD117) over-expressing neoplasms. As the treatment eligibility for these drugs hinges on CD117 expression, Kit immunostaining has recently been widely examined in various tumours. There are only limited data in the literature on the expression of c-kit expression in Wilms' Tumour. We examined CD117 expression in Wilms' tumour in order to correlate this marker with clinico-pathological data and to clarify its prognostic impact. METHODS This study included 40 cases of Wilms' tumour. Sections from paraffin-embedded tumour samples were immunostained by standard ABC technique using c-kit polyclonal antibody with antigen retrieval. CONCLUSIONS In the case of C-kit positive examples, the staining was focal, with patch distribution. On univariate analysis, significantly higher c-kit expression was observed in neoplasms in a more advanced stage of development than those in a less advanced stage (p=0.0055). In addition, over-expression of this marker was significantly correlated with the death of patients (p=0.0294) and recurrences of disease (p=0.0118). Moreover, all our Wilms' tumour anaplastic subtypes showed over-expression of c-kit and this was significantly higher than in favourable histology examples (p=0.0182). The results of multivariate analysis, instead, did not reveal any correlation of c-kit expression and prognosis. In our opinion these results could be due to the number of cases considered which is not particularly high. However, it seems likely that c-kit expression could be a secondary event related to tumour progression and could be influenced by chemotherapy and unfavourable histology.