Post therapy Wilms tumour or ectopic immature renal tissue: A pathologist's diagnostic dilemma

Post chemotherapy Wilms Tumour (PCWT) is a diagnostic conundrum both for the clinician and the pathologist, in view of its morphological similarity with ectopic immature renal tissue (EIRT). However, due to their varying prognoses and different lines of management, it is important to distinguish between the two. Here, we discuss clinical presentation and pathology of a case of PCWT, arising in a horse shoe deformity of the kidney in a 5 year old girl. The discussion focuses on the pathogenesis of Extra Renal Wilms Tumour (ERWT) as well as its distinguishing morphological features and chemotherapy induced changes in Wilms tumour.