This tumor growth
in a healthy kidney tissue and form a pseudo-capsule. It has macroscopic
boundaries which is clearly covered by kidney tissue. The development of this
tumor start by forming the pseudo-capsule, followed by infiltration into the
kidney tissue itself, then spread into perirenal tissue and start to spread or
metastasize. The spreading of the tumour can occur through connective tissu,
hematogenously and lymphogenously. For coonective tissu, it iccur through perirenal
fat tissue then to the peritoneum and abdominal organs (contralateral kidney,
liver, etc.). For hematogenous route, it occurs after tumor growth into the
renal vein then spread especially to the lungs (90%) then to the brain and
bones. Through lymphogenous route, the spread occurs in regional glands around abdominal
aorta or in mediastinum.

Wilms tumor is
derived from the metastatic blastema primitive tissue and is characterized by a
diverse image histopathologically. Classic Wilms tumor is composed of
persistent blastema, dysplasia tubules (epithelium), and supporting mesenchymal
tissue (stroma). The presence of epithelial cells, blastema, and stroma in one
histological picture is called triphasic and is a characteristic of classic
Wilms tumor. Each type of cell can display spectrum of differentiation,
generally replicating the variety stage of renal embryogenesis. The proportion
of each cell type can also vary between one tumors with another 11. Some
Wilms tumors are biphasic or even monomorphic. Histologically, Wilms tumor can
be both favorable (well differentiated) and unfavorable or anaplastic (poorly
differentiated). The histologic picture of well differentiated tumor is often
found (89%) and is characterized by the presence of three components as already
stated previously epithelial cells, blastema, and stroma. Histologic features of
poorly differentiated are less common (less than 10%) and illustrated by the presence
of anaplasia. Anaplasia is characterized by the presence of a giant polypoid
nucleus in tumor samples. Few criteria must be meet to determine the presence
of anaplasia. First, the nucleus must have a primary diameter of at least three
times of adjacent cells, with increased chromatin. Second, it must have multipolar
features or other identifiable polypoid mitotic features.

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Anaplasia can be
focal or diffuse. Criteria for differentiating focal and diffuse anaplasia
depending on the spread of anaplasia. Focal anaplasia is indicated by changes
in anaplastic nucleus which are limited in primary tumors. This definition
limits focal anaplasia to one or several separate loci in primary and tumor
without anaplasia or other atypical nuclei. The diagnosis of diffuse anaplasia
must a few the criteria. First is extrarenal anaplasia, including vessels blood
in the renal sinuses, extracapsular infiltration, gland metastases or distant
metastases. Second is anaplasia on randomized biopsy of the specimen. Third, acute
anaplasia in one region of the tumor, but with the pleomorphism of the nucleus
extreme approach to other naplasia criteria on lesions. Fourth, anaplasia in
more than one tumor preparation, except it is known that each preparation shows
anaplasia originating from the same region on the tumor and the focus of
anaplasia on some amounts of preparations little and surrounded entirely by
nonanaplastic tumors.

Wilms tumor is a
primary renal tumor most commonly found in childhood. Clinical symptoms can be
found between another belly bulge due to mass abdomen, hematuria, hypertension,
anemia, pain stomach, fever, and signs of a channel infection urine. Abdominal
ultrasound is an imaging technique the most often done to enforce the diagnosis
of Wilms tumor. Management including surgery, radiotherapy and chemotherapy.