Скачать или смотреть PATHOLOGY PRACTICAL || WILMS TUMOR with notes and viva questions || NEPHROBLASTOMA in full detail

Wilms tumor, or nephroblastoma, is the most common renal cancer in the pediatric age group. It is also the most common pediatric abdominal cancer and the fourth most common pediatric cancer overall. Wilms tumor is typically found in children younger than five years old.



The cause of Wilms tumor is not precisely known, but it is believed to be due to genetic alterations that deal with the normal embryological development of the genitourinary tract. Some of the genetic markers that have been associated with Wilms tumor include WT1, CTNNB1, and WTX gene alterations that have been found in about 1/3 of all Wilms tumors. Other genes associated with Wilms tumor include TP53 and MYNC. A poorer prognosis has been linked to TP53 and with the loss of heterozygosity at chromosomes 1p, 1q, 11p15, and 16q.

Only about 1% of Wilms patients have a relative with the disease who is typically not a parent.

Wilms is thought to develop from persistent metanephric tissue or nephrogenic rests. These may occur in 1% of infantile kidneys but typically regress during childhood. These abnormal metanephric cells are found in up to 100% of cases of bilateral Wilms but only 35% of unilateral tumors.

Hemihypertrophy and aniridia as well as a variety of urological disorders like cryptorchidism, horseshoe kidney, and hypospadias, are associated with the malignancy although it is unlikely they play any role in actual carcinogenesis.

The bilateral disease represents only about 5% of all patients with Wilms tumor and is more commonly found in girl.




Grossly, Wilms tumors are usually well-circumscribed and have a pseudo-capsule.

Histologically, Wilms is divided into "favorable" and "unfavorable" histologies.

"Favorable" Histology: Ninety percent of Wilms tumors will demonstrate "favorable" histology, which generally has a better prognosis. Classical histological features of a "favorable" Wilms tumor include a triphasic pattern of blastema, epithelial, and stromal tissues. The blastema is the most undifferentiated and possibly the most malignant component. It consists of collections of small, round blue cells with very active mitotic activity and overlapping nuclei.

The epithelial component can demonstrate wide variations in differentiation from an early tubular formation with primitive epithelial rosette-like structures to differentiating tubules or glomeruli-like structures, representing nephrogenesis at different developmental stages.

The stromal component may include densely packed undifferentiated mesenchymal cells or loose cellular myxoid areas. The latter areas may be difficult to distinguish from non-tumorous stroma associated with chemotherapy-induced change. Heterologous differentiation of neoplastic stroma in the form of well-differentiated smooth or skeletal muscle cells, fat tissue, cartilage, bone, and even glial tissue is present in some cases, especially in tumors that have undergone preoperative chemotherapy.

Even with "Favorable" histology, the loss of heterozygosity at 1p and 16q loci tend to have a worse prognosis. For this reason, when Wilms tumor tissue is available, it should be checked cytogenetically for 1p and 16q deletions.

"Unfavorable" Histology: Wilms tumors with "unfavorable" histology will demonstrate much higher degrees of anaplasia and are associated with a relatively poorer prognosis and survival.

Anaplasia is histologically defined as hyperchromatic, pleomorphic nuclei that are three times larger than adjacent cells and have abnormal mitotic figures. Anaplasia is associated with a poor response to treatment.



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