<prompt> A 7 year old boy with left renal mass had bone pain and was detected to have bone metastatic deposits. The most likely renal tumor is :Favorable histology Wilms tumorRenal cell carcinomaClear cell sarcomaRhabdoid tumor  <response>: Clear cell carcinoma is a histological subtype of wilms tumor which frequently metastasize to bone In conventional wilmss tumor bone metastasis is rare.Histology of wilms tumor Wilms 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. 