Diagnosis of Wilms' tumor

The scope of necessary studies in case of suspected Wilms tumor

Anamnesis	Family history of cancer, congenital defects
Medical examination	Detection of congenital anomalies (aniridia, hemihypertrophy, urogenital anomalies), measurement of blood pressure
Complete blood count	Presence or absence of polycythemia
General urine analysis	Presence or absence of microhematuria
Biochemical blood test	Serum urea, creatinine, uric acid, glutaminoxaloacetate kinase, glutamyl pyruvate kinase, lactate dehydrogenase and alkaline phosphatase activity
Evaluation of hemostasis	Prothrombin time, thromboplastin time, fibrinogen concentration, bleeding time (if elevated, determine the concentration of factor VIII, von Willebrand factor antigen)
Assessment of cardiac activity	Electrocardiography and echocardiography are indicated for all patients receiving anthracyclines (echocardiography also allows detection of tumor thrombus in the right atrium)
Ultrasound examination of abdominal organs	-
CT scan of abdominal organs with targeted examination	Allows to clarify the presence and function of the contralateral kidney, exclude bilateral kidney damage, involvement of the main vessels and lymph nodes in the tumor process, and determine tumor infiltration of the liver
X-ray of the chest organs (in three projections)	-
CT scan of the chest organs	Allows detection of small metastases that may be hidden by ribs or the diaphragm and missed during chest X-ray examination
Radioisotope study of the skeleton	The study is only indicated in cases of clear cell renal sarcoma, which can metastasize to bone.
CT or MRI of the brain	The study is indicated in the case of rhabdoid tumors, often associated with CNS tumors, and clear cell sarcoma of the kidney, which can metastasize to the brain.
Chromosomal analysis of peripheral blood cells	The study is indicated for congenital anomalies (aniridia, Beckwith-Wiedemann syndrome, hemihypertrophy)

At the preoperative stage, it is necessary to examine the function of the unaffected contralateral kidney, exclude metastases in the lungs, and the presence of tumor thrombi in the inferior vena cava.

Staging of Wilms' tumor

Clinicopathological staging of Wilms tumor

Stage	Tumor characteristics
I	The tumor is limited to the kidney and completely removed, the renal capsule is intact. There is no tumor rupture before surgery and during removal. The tumor is removed radically, marginally tumor tissue is not determined
II	The tumor invades the kidney capsule, but is completely removed, regional tumor spread is detected (i.e. tumor growth into the soft tissues surrounding the kidney). The ureters are not involved in the tumor process, there is no invasion of the renal pelvis. There are no signs of tumor after surgery
III	Residual tumor limited to the abdominal cavity without hematogenous metastases, as well as the presence of any of the following factors. A. Morphologically confirmed involvement of lymph nodes outside the para-aortic zone in the tumor process. B. Diffuse peritoneal tumor cell contamination with ipsilateral dissemination before or during surgery or with dissemination of tumor cells throughout the peritoneum due to tumor rupture before or during surgery. B. Peritoneal tumor implants. G. Postoperatively, residual tumor is determined macroscopically or microscopically. D. The tumor is not completely removed due to infiltration of vital structures.
IV	Hematogenous metastases: metastases to the lungs, liver, bones, brain
V	Bilateral tumor at diagnosis: examination is required on each side, according to the criteria for diagnosis at the preoperative stage. This stage is divided into a number of substages. A. Damage to one of the poles of both kidneys. B. Lesion of one kidney with involvement of the organ hilum in the tumor process (total or subtotal) and one of the poles of the second kidney. C. Lesion of both kidneys with involvement of the hilum (total or subtotal)

Pathomorphological characteristics of Wilms tumor

Wilms tumor originates from primitive metanephric blastema cells and is characterized by a variety of histological patterns. The classic variant of Wilms tumor is represented by blastema cells and dysplastic epithelial tubules, contains mesenchyme or stroma. The detection of epithelial germ cells and stromal cells in tumor tissue led to the emergence of the term "three-phase histological pattern" characterizing the classic variant of Wilms tumor. Each type of Wilms tumor cells can differentiate in various directions, repeating the stages of renal embryogenesis. The ratio of cell types in tumor tissue in different patients may differ significantly.

It should be noted that clear cell renal sarcoma and rhabdoid renal tumor are not variants of Wilms tumor.

Anaplastic Wilms' tumor

The presence of cellular anaplasia in Wilms' tumor is the only criterion for an "unfavorable" histological picture. Focal anaplasia differs from diffuse anaplasia by the degree of distribution in the tumor tissue. In the first case, anaplastic nuclei are focally limited to one or more areas without anaplasia. To establish a morphological diagnosis of diffuse anaplasia, it is necessary to have anaplastic cells in any extrarenal localization (ureters, extracapsular infiltrate, regional or distant metastases), anaplasia in the tumor biopsy (in more than one section).

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