Wilms’ Tumor

Published on 21/03/2015 by admin

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Last modified 21/03/2015

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Chapter 84 Wilms’ Tumor


Wilms’ is typically a large, encapsulated, single tumor arising from the renoblast cells located in the renal parenchyma. A membranous capsule usually encloses the tumor. Wilms’ tumors may be multifocal, extend to surrounding structures, involve both kidneys, cause obstruction of the inferior vena cava, invade local retroperitoneal lymph nodes, and/or obstruct the intestines. Metastasis most often occurs in the lungs, followed by the liver and the contralateral kidney, and in rare cases spreads to the bone. Ten percent of Wilms’ patients have associated congenital anomalies such as WAGR syndrome (Wilms’, aniridia—absence of pupils, genitourinary [GU] abnormalities, and mental retardation) hypospadias, cryptorchidism, Denys-Drash syndrome (pseudohermaphroditism, GU ambiguity), cardiac malformations, and aniridia. Another 10% have phenotypic or overgrowth syndromes (syndromes characterized by overgrowth of organs or features) such as hemihypertrophy, and Simpson-Golabi-Behmel and Beckwith-Wiedemann. Children with overgrowth syndromes should be screened for Wilms’ using renal ultrasound every 3 months until they are 10 years of age.

Wilms’ tumor grows rapidly, and typically it is very large when detected. Tissue type varies from “favorable” to “unfavorable” and is the most significant prognostic characteristic. Children with favorable histologic characteristics have 95% survival. Within this favorable category is a cystic, partially differentiated nephroblastoma variant that has 100% survival with surgery alone. Unfavorable histologic characteristics include various degrees of anaplasia (e.g., enlarged nucleus; hyperploidy, which increases the potential for metastasis) that account for more aggressive disease and are more common in children over 2 years of age. The more areas of anaplasia seen, the more aggressive the tumor. Clear-cell sarcoma and rhabdoid tumors are aggressive renal tumors and are not classified as Wilms’ tumor. Congenital mesoblastic nephromas are benign renal tumors that are also not considered in the Wilms’ family of tumors. Nephroblastomatosis is a focus of cells that, if found, indicate a precursor lesion with a higher risk of development of tumor in the contralateral kidney. These are resting cells, also known as “nephrogenic rests,” with a propensity to become Wilms’.

A small percentage of Wilms’ tumors are hereditary. Hereditary forms account for the majority of bilateral Wilms’. Chromosomal abnormalities linked to specific genes such as WT1 and WT2 are now known to be associated with the predisposition to Wilms’ tumor. WT1 gene has been found on short arm of chromosome 11p13. WT2 has been mapped to 11p15 location and is associated with Beckwith-Weidemann syndrome. These genetic mutations can occur sporadically or be inherited.