Clear cell carcinoma is a histological subtype of wilm’s tumor which frequently metastasize to bone (In conventional wilms's tumor bone metastasis is rare). Histology of wilms tumorWilms tumor is a complex mixed embryonal neoplasm, comprises three elements : -Blastenia. Mesenchyme. Epithelium.On the basis of outcome Wilms tumor has been classified into two histological subtypes.Favorable histology :It is the conventional form and carries good prognosis. Comprises blastoma, epithelial and stromal elements. Devoid of anaplasia or ectopia. Brain and bone metastasis is rare. Metastasis may occur to lung.Unfavorable histology :Characterized by marked enlargement of nuclei, hyperchromatism, and multipolar mitotic figures. Anaplasia is present. Clear cell sarcoma is a subtype of the unfavorable form and usually metastasizes to bone.Note :Rhabdoid tumor, which may metastatize to the brain, is no longer classified as a subtype of wilms tumor.