Sarcomatous tumours of the kidney

Abstract

Variable patterns of behaviour in relation to ‘Wilms’ tumour’ had been recognized for many years ¹. The identification of several new entities then led to gradual attrition of the tumour category. Congenital mesoblastic nephroma was the first such entity to be identified. Others followed, including a small subgroup with a distinct microscopy that had been recognized earlier for its propensity to metastasize to bone. Subsequently, the first National Wilms’ Tumor Study (NWTS) reported three sarcomatous patterns associated with a poor outcome². These patterns were referred to as rhabdomyosarcomatoid, clear-cell pattern and the hyalinizing pattern. The term ‘rhabdomyosarcomatoid’ was based on the light microscopic features that suggested muscle differentiation; ultrastructural studies, however, subsequently failed to confirm muscle differentiation and the tumours were renamed rhabdoid tumours³. Tumours with a similar microscopic pattern were later described in extrarenal locations⁴; their precise relationship to the renal tumours has yet to be clarified⁵.