title: Renal metastasis from thyroid carcinoma: a case report.
abstract: BACKGROUND
  Renal metastases of thyroid carcinomas occur rarely and represent about 3% of all metastases to the kidney, with only 23 single case study reports in the English language literature.
  
  
  METHODS
  A 77-year-old man presented with gross hematuria. CT scan showed a posterior and cortico-sinusal mass in the right kidney measuring 5 x 3 cm. On gross examination the kidney was occupied by a lobulated mass measuring 4.5 cm in its greatest dimension. Microscopically, there was a papillary and follicular proliferation with colloid-like materials in the intrafollicular space. The strong positive immunohistochemical stain of thyroglobulin and thyroid transcription factor-1 confirmed the origin of thyroid gland and the diagnosis of renal metastasis of thyroid carcinoma.
  
  
  CONCLUSIONS
  Although rare, the renal metastasis of a thyroid carcinoma is a diagnostic to consider even if the renal mass is unilateral and the patient has no history of thyroid surgery. The main differential diagnostic is the primitive thyroid-like follicular carcinoma of the kidney. Immunohistochemistry often leads to the right diagnosis, which is crucial for the management of the patient. Renal metastases of thyroid carcinomas are rare and often present as a primitive unilateral renal mass.
authors.forename: Justine
authors.initials: J
authors.lastname: Varinot
authors.forename: Fabrice
authors.initials: F
authors.lastname: Ménégaux
authors.forename: Marc-Olivier
authors.initials: MO
authors.lastname: Bitker
authors.forename: Eva
authors.initials: E
authors.lastname: Compérat
mesh_terms: D018263:Adenocarcinoma, Follicular / Q000378:metabolism / Q000556:secondary*; D000368:Aged; D001706:Biopsy; D003937:Diagnosis, Differential; D006801:Humans; D007150:Immunohistochemistry; D007680:Kidney Neoplasms / Q000378:metabolism / Q000556:secondary*; D008297:Male; D009687:Nuclear Proteins / Q000378:metabolism; D013964:Thyroid Neoplasms / Q000378:metabolism / Q000473:pathology*; D000074482:Thyroid Nuclear Factor 1; D014157:Transcription Factors / Q000378:metabolism
chemical_list: C000614412:NKX2-1 protein, human; D009687:Nuclear Proteins; D000074482:Thyroid Nuclear Factor 1; D014157:Transcription Factors