This tumor growthin a healthy kidney tissue and form a pseudo-capsule. It has macroscopicboundaries which is clearly covered by kidney tissue. The development of thistumor start by forming the pseudo-capsule, followed by infiltration into thekidney tissue itself, then spread into perirenal tissue and start to spread ormetastasize. The spreading of the tumour can occur through connective tissu,hematogenously and lymphogenously. For coonective tissu, it iccur through perirenalfat tissue then to the peritoneum and abdominal organs (contralateral kidney,liver, etc.).

For hematogenous route, it occurs after tumor growth into therenal vein then spread especially to the lungs (90%) then to the brain andbones. Through lymphogenous route, the spread occurs in regional glands around abdominalaorta or in mediastinum.Wilms tumor isderived from the metastatic blastema primitive tissue and is characterized by adiverse image histopathologically. Classic Wilms tumor is composed ofpersistent blastema, dysplasia tubules (epithelium), and supporting mesenchymaltissue (stroma). The presence of epithelial cells, blastema, and stroma in onehistological picture is called triphasic and is a characteristic of classicWilms tumor. Each type of cell can display spectrum of differentiation,generally replicating the variety stage of renal embryogenesis. The proportionof each cell type can also vary between one tumors with another 11.

SomeWilms tumors are biphasic or even monomorphic. Histologically, Wilms tumor canbe both favorable (well differentiated) and unfavorable or anaplastic (poorlydifferentiated). The histologic picture of well differentiated tumor is oftenfound (89%) and is characterized by the presence of three components as alreadystated previously epithelial cells, blastema, and stroma. Histologic features ofpoorly differentiated are less common (less than 10%) and illustrated by the presenceof anaplasia. Anaplasia is characterized by the presence of a giant polypoidnucleus in tumor samples. Few criteria must be meet to determine the presenceof anaplasia.

First, the nucleus must have a primary diameter of at least threetimes of adjacent cells, with increased chromatin. Second, it must have multipolarfeatures or other identifiable polypoid mitotic features.Anaplasia can befocal or diffuse.

Criteria for differentiating focal and diffuse anaplasiadepending on the spread of anaplasia. Focal anaplasia is indicated by changesin anaplastic nucleus which are limited in primary tumors. This definitionlimits focal anaplasia to one or several separate loci in primary and tumorwithout anaplasia or other atypical nuclei. The diagnosis of diffuse anaplasiamust a few the criteria. First is extrarenal anaplasia, including vessels bloodin the renal sinuses, extracapsular infiltration, gland metastases or distantmetastases. Second is anaplasia on randomized biopsy of the specimen.

Third, acuteanaplasia in one region of the tumor, but with the pleomorphism of the nucleusextreme approach to other naplasia criteria on lesions. Fourth, anaplasia inmore than one tumor preparation, except it is known that each preparation showsanaplasia originating from the same region on the tumor and the focus ofanaplasia on some amounts of preparations little and surrounded entirely bynonanaplastic tumors.Wilms tumor is aprimary renal tumor most commonly found in childhood. Clinical symptoms can befound between another belly bulge due to mass abdomen, hematuria, hypertension,anemia, pain stomach, fever, and signs of a channel infection urine.

Abdominalultrasound is an imaging technique the most often done to enforce the diagnosisof Wilms tumor. Management including surgery, radiotherapy and chemotherapy.