It is malignant neoplasm arising from nephrogenic blastemal cells
Precursor lesion for the wilms tumor are – Nephrogenic rests
Age group – less than 10 years ( peak 5 – 6 yrs)
Shows slight female predominance
Chromosomal abnormality is consistent deletion of chromosome 11p13. Gene on this location is designated as WT1. This gene plays a major role in renal and gonadal development.
Associated with WAGR syndrome, Denys Drash syndrome and Beckwith weidmann syndrome
Clinical features
Abdominal mass (commonest sign)
Haematuria
Pain abdomen
Hypertension
Gross
Unilateral (10% bilateral), solitary, well circumscribed lesion.
Cut section uniform, pale gray or tan – pink and soft in consistency (Fish flesh like)
Tumor is firm if stromal component predominates
Microscopy
Tumor shows Triphasic components which are blastemal component, epithelial component, and stromal component
Biphasic and monophasic patterns can also occur.
Blastemal component – cells resemble condensed mesenchyme from which the kidney develops. Cells are small closely packed mitotically active with minimal differentiation. They are polygonal or rounded or may be elongated having small nuclei with coarse chromatin and small nucleoli. Reliable feature of blastemal cells is the nuclear overlapping. Many atypical mitotic figures are seen. Different patterns of blastemal cells are serpentine, basaloid, nodular or diffuse pattern. Diffuse blastemal patterns is associated with invasive growth pattern.
Epithelial component – Epithelial component as primitive rosette like structures. Tubular or papillary structures which represent various stages of normal nephrogenesis. Glomerular like structures with capillaries are seen. Heterologous epithelial differentiation showing the elements like mucinous, squamous epithelium or ciliated epithelium can be present.
Stromal component – myxoid or spindle cells resembling embryonic mesenchyme. smooth muscle, fibroblast, and skeletal muscle differentiation can be seen. Primitive myoblastic elements resembling cambium layer of botryoid embryonal rhabdomyosarcoma can be seen. Other stromal differentiation are adipose, cartilage, osteoid, mature ganglion cells, neuroglial tissue.
Metastasis
Tumor spreads by hematogenous route and the common organ involved in the metastasis is lung
Treatment and prognosis
Treatment is surgical removal followed by radiotherapy
Poor prognostic factors are
Multifocality
Anaplastic histology
Loss of genetic material on chromosomes 11q and 16q
Gain on chromosomes 1q
Other primary tumors which can develop in patients with wilms tumor due to either presence of germline mutations or radiation are
Bone and soft tissue sarcomas
Leukemia
Lymphoma
Breast cancer
References :
Robbins and Cotrans: Pathologic basis of diseases.8th edition
