title: [CT findings of metastatic and primary neoplasms of the kidney: a comparative study].
abstract: OBJECTIVE
  To study CT findings of renal metastases and compare them with primary renal cell carcinoma.
  
  
  METHODS
  CT features of eleven cases of renal metastases and one hundred cases of primary renal cell carcinoma confirmed by histopathology were studied and compared. The metastastic tumors arised from lung carcinoma in 6 cases, esophagus carcinoma in 2 cases and one in each of adrenal cortical carcinoma, testis seminoma and unknown primary tumor.
  
  
  RESULTS
  Renal metastases accounted for 3.7% of all malignant tumors of the kidney. The ratio of renal metastases to second primary renal carcinoma was 1:1. On CT, the renal metastases appeared as diffusely invasive, ill-definded mass (63.6%), 18.2% of the neoplasms were multiple, without or less exophytic (81.8%) and without or with minimal enhancing on postcontrast scan (100%). The tumor invaded the pelvocalyceal system (72.7%). In contrast, the primary renal cell carcinomas were nodular, rounded or lobulated and more exophytic mass with well-defined border and regular contours (87.0%). Moderate to high enhancing postcontrast (80.7%) was observed with obvious necrosis (60.2%), foci of calcification (15.0%) and invasion of the renal vein and inferior vena cava (7.0%).
  
  
  CONCLUSIONS
  Contrast-enhanced CT is helpful in the differential diagnosis of renal metastases from primary renal cell carcinoma. But for those showing single, more exophytic mass with well-defined border and intense enhancing postcontrast, the correct diagnosis depends on histopathology.
authors.affiliation: Cancer Institute (Hospital), Chinese Academy of Medical Sciences, Peking Union Medical College, Beijing 100021.
authors.forename: J
authors.initials: J
authors.lastname: Dai
authors.forename: L
authors.initials: L
authors.lastname: Zhu
authors.forename: X
authors.initials: X
authors.lastname: Zhang
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D007680:Kidney Neoplasms / Q000000981:diagnostic imaging* / Q000556:secondary; D008297:Male; D008875:Middle Aged; D014057:Tomography, X-Ray Computed