title: Mixed Epithelial and Stromal Tumor of the Kidney with Sarcomatous Transformation Metastatic to the Lung. A Case Report.
abstract: BACKGROUND
  Malignant transformation of mixed epithelial and stromal tumor (MEST) of the kidney is a very rare entity. We report an unusual case with a review of the literature.
  
  
  METHODS
  A 25-year-old woman underwent surgery for an 8-cm biphasic renal tumor, which was diagnosed as MEST of the kidney. High cellularity, mitoses, and nuclear atypia seen in the stromal component were compatible with a sarcomatous transformation in MEST. The patient also had pulmonary metastatic nodules that were resected 2 months after the nephrectomy. Metastatic pulmonary tumors were morphologically identical to the sarcomatous component of the renal tumor and showed pulmonary epithelial hyperplasia with a phyllodes-like pattern.
  
  
  CONCLUSIONS
  Although MEST of the kidney is known as a benign tumor, malignant transformation, mostly sarcomatous type, should be considered in the diagnosis.
authors.forename: Yasemin
authors.initials: Y
authors.lastname: Ozluk
authors.forename: Sule Ozturk
authors.initials: SO
authors.lastname: Sari
authors.forename: Nalan Turan
authors.initials: NT
authors.lastname: Guzel
authors.forename: Pinar
authors.initials: P
authors.lastname: Firat
authors.forename: Fatih
authors.initials: F
authors.lastname: Akbulut
authors.forename: Isin
authors.initials: I
authors.lastname: Kilicaslan
mesh_terms: D000328:Adult; D002471:Cell Transformation, Neoplastic / Q000473:pathology*; D005260:Female; D006801:Humans; D007680:Kidney Neoplasms / Q000473:pathology*; D008175:Lung Neoplasms / Q000556:secondary*; D018193:Neoplasms, Complex and Mixed / Q000556:secondary*