Late recurrence of Wilms' tumour with exclusive skeletal muscle phenotype 23 years after primary diagnosis.

A late recurrence of Wilms' tumour (WT) 23 years after the primary diagnosis is described. The primary tumour occurred in a 10-month-old girl and showed various degrees of differentiation, including skeletal muscle phenotype. A postoperative chemotherapy was performed. Twenty-three years after the surgery, the tumour relapsed: the lesion was exclusively composed of mature skeletal muscle elements (diffuse and intense desmin reactivity) derived from the primary tumour as confirmed by WT1 immunoreactivity. Chemotherapy and radiotherapy have been reported previously to ablate the immature components of WT; especially, chemotherapy can modify the histological type, reducing the immature elements while leaving mature cells unaffected. We can hypothesise that both morphological and molecular features of the tumour as well as the effect of therapy can influence a tumour relapse in WT. The latter results in a high degree of differentiation and a long disease-free interval after the first diagnosis.