title: Cellular mesoblastic nephroma (infantile renal fibrosarcoma): institutional review of the clinical, diagnostic imaging, and pathologic features of a distinctive neoplasm of infancy.
abstract: BACKGROUND
  Cellular mesoblastic nephroma has been associated with a more aggressive course than classic mesoblastic nephroma, including local recurrences and metastases.
  
  
  OBJECTIVE
  To define the clinicopathologic and imaging features distinguishing cellular from classic mesoblastic nephroma.
  
  
  METHODS
  Retrospective review of clinical charts and imaging studies of ten children with mesoblastic nephroma from 1996 to 2007 at a large children's hospital.
  
  
  RESULTS
  In six children the mesoblastic nephroma was pure cellular, in two mixed, and in two classic. The mean ages at diagnosis were 107 days for those with the cellular form, and 32 days for those with the classic form. Hypoechoic or low-attenuation regions representing necrosis or hemorrhage were found in all children with the cellular form and in none of those with the classic form. Hypertension was present in 70% and hypercalcemia in 20% of the children and resolved following nephrectomy. Two cellular tumors encased major abdominal vessels. Local recurrence and metastases occurred within 6 months of tumor resection in two children with the cellular form. Intraspinal extension and intratumoral pseudoaneurysm were seen in one child with the cellular form. The cellular tumors shared histopathologic features with infantile fibrosarcoma (IFS), and RT-PCR testing in two children with the cellular form revealed the t(12;15) ETV6-NTRK3 gene fusion common to IFS.
  
  
  CONCLUSIONS
  Distinct from the classic form, cellular mesoblastic nephroma is more heterogeneous in appearance on imaging, tends to be larger and present later in infancy, and can exhibit aggressive behavior including vascular encasement and metastasis. Intraspinal extension and intratumoral pseudoaneurysm are previously unreported findings encountered in our cellular mesoblastic nephroma series. The shared histopathology and translocation gene fusion support the concept of cellular mesoblastic nephroma as the renal form of IFS.
authors.affiliation: Department of Radiology, Ege University Medical Faculty, AD Bornova, Izmir 35100, Turkey. petek.bayindir@ege.edu.tr
authors.forename: Petek
authors.initials: P
authors.lastname: Bayindir
authors.forename: Robert Paul
authors.initials: RP
authors.lastname: Guillerman
authors.forename: M John
authors.initials: MJ
authors.lastname: Hicks
authors.forename: M Murali
authors.initials: MM
authors.lastname: Chintagumpala
mesh_terms: D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007680:Kidney Neoplasms / Q000000981:diagnostic imaging*; D008297:Male; D018201:Nephroma, Mesoblastic / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000379:methods*