title: Metanephric adenoma and solid variant of papillary renal cell carcinoma: common and distinctive features.
abstract: OBJECTIVE
  To evaluate morphological and immunohistochemical (IHC) features helpful in distinguishing metanephric adenoma (MA) from solid papillary renal cell carcinoma (s-PRCC).
  
  
  RESULTS
  We present a detailed study of 21 MA and 23 s-PRCC. The two entities exhibited significant similarities, both being well-circumscribed tumours composed of tightly packed small cells arranged in solid sheets or ill-defined tubules, often presenting glomeruloid bodies, psammoma bodies and dystrophic calcification, and showing overlapping immunoreactivity for S100, CD57 and CK7. Conversely, most MA were non-encapsulated, whereas most s-PRCC showed a thick fibrous pseudocapsule; MA cells had scanty cytoplasm and a high nuclear:cytoplasmic ratio in comparison to s-PRCC, where occasional tumour cells showed abundant cytoplasm and high nuclear grade. Polypoid branching fronds were common in MA, but absent in s-PRCC; multifocality and papillary hyperplasia/adenoma were seen only in s-PRCC. MA were positive for WT1 and negative for EMA and alpha-methylacyl-CoA racemase (AMACR); s-PRCC were positive for EMA and AMACR and negative for WT1.
  
  
  CONCLUSIONS
  Despite overlapping features, careful morphological and architectural evaluation should result in accurate diagnosis of most MA and s-PRCC. In challenging cases, IHC stains for WT1, EMA and AMACR may help in distinguishing these two entities.
authors.affiliation: Pathology and Laboratory Medicine Institute, Cleveland Clinic, Cleveland, OH, USA.
authors.forename: Mariana
authors.initials: M
authors.lastname: Mantoan Padilha
authors.forename: Athanase
authors.initials: A
authors.lastname: Billis
authors.forename: Daniela
authors.initials: D
authors.lastname: Allende
authors.forename: Ming
authors.initials: M
authors.lastname: Zhou
authors.forename: Cristina
authors.initials: C
authors.lastname: Magi-Galluzzi
mesh_terms: D000236:Adenoma / Q000175:diagnosis / Q000378:metabolism / Q000473:pathology*; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000378:metabolism; D018959:CD57 Antigens / Q000378:metabolism; D002292:Carcinoma, Renal Cell / Q000175:diagnosis / Q000378:metabolism / Q000473:pathology*; D002648:Child; D002675:Child, Preschool; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D053552:Keratin-7 / Q000378:metabolism; D007680:Kidney Neoplasms / Q000175:diagnosis / Q000378:metabolism / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D018396:Mucin-1 / Q000378:metabolism; D019998:Racemases and Epimerases / Q000378:metabolism; D009418:S100 Proteins / Q000378:metabolism; D025721:WT1 Proteins / Q000378:metabolism; D055815:Young Adult
chemical_list: D014408:Biomarkers, Tumor; D018959:CD57 Antigens; C507497:KRT7 protein, human; D053552:Keratin-7; C060192:MUC1 protein, human; D018396:Mucin-1; D009418:S100 Proteins; D025721:WT1 Proteins; C583751:WT1 protein, human; D019998:Racemases and Epimerases; C108352:alpha-methylacyl-CoA racemase