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Papillary Adenoma of the Kidney

Definition

  • Benign renal cortical neoplasm with papillary/tubular pattern measuring ≤0.5 cm

Diagnostic Criteria

  • Among renal cell neoplasms, the term adenoma is reserved for those with a papillary or tubular pattern
    • No equivalent benign lesion is recognized for clear cell, chromophobe, collecting duct or medullary carcinomas
  • All of the following criteria must be fulfilled
    • Must have only papillary or tubular architecture
      • May not have clear or chromophobe cells
        • All such lesions should be considered carcinomas
    • May be no larger than 0.5 cm
      • Any larger lesion should be considered carcinoma
    • Must be low grade cytologically
      • Fuhrman/nuclear grade 1 or 2
        • Any higher grade lesion should be considered carcinoma
      • Absent to inconspicuous nucleoli
      • Mitotic figures very rare
    • Microscopically localized but not encapsulated
      • May be multiple
        • If numerous, consider adenomatosis
          • Generally >50 in reported cases, but number required is not well defined
          • Significance is not well characterized
      • May have an irregular interface with surrounding tissue
        • No desmoplastic response
    • Lining cells usually small with scant pale cytoplasm
    • Psammoma bodies and foamy macrophages may be seen
    • Similar changes in lining of Bowman capsule termed "adenomatoid metaplasia of Bowman capsule"

John P Higgins MD
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342

Original posting:: January 24, 2011

Supplemental studies

Immunohistology

  • Most cases positive for racemase and vimentin

Genetic Study

  • Changes similar to those of papillary carcinomas (Kovacs 1991)
    • Trisomy 7/17 and loss of Y chromosome

Differential Diagnosis

Papillary Renal Cell Carcinoma Renal Adenoma
>0.5 cm diameter Papillary lesion ≤0.5 cm REQUIRED
May have any nuclear grade Nuclear grade 1 or 2 REQUIRED

Conventional Clear Cell Renal Cell Carcinoma Renal Adenoma
No size cutoff for clear cell tumors Papillary lesion ≤0.5 cm, clear cells not permitted
May be high or low grade Must be no higher than grade 2
CK7, AMACR/racemase/P504S neg to focal CK7, AMACR/racemase/P504S pos

Two types of renal cell carcinoma are associated with end stage renal disease

  • One is composed of cells with clear cytoplasm, the other of cells with high grade nuclear features
    • Neither feature is permitted in renal adenomas

Grading / Staging

Grading

  • Does not apply as these are benign neoplasms
    • However, by definition they have grade 1 or 2 nuclei (see below)

Staging

  • Does not apply
  • Most commonly cited grading scheme is that of Fuhrman
    • Requires simultaneous assessement of three features: nulear size, shape and nucleoli
      • Nuclear size may be subject to fixation variables and difficult to measure
      • No provision for cases with discrepant grade features
      • Poor interobserver agreement
  • We and others find a simplified version based primarily on nucleolar prominence to be more practical
    • Simplified Fuhrman Grading
    Grade 1 Small, round, dark lymphocyte-like nuclei with without visible nucleoli
    Grade 2 Inconspicuous nucleoli, visible only at 200-400X (nuclei usually small and uniform with open, finely granular chromatin)
    Grade 3 Prominent nucleoli, easily visible at 100X (nuclei usually mildly to moderately pleomorphic)
    Grade 4 Markedly pleomorphic, bizarre nuclei, giant cells, multiple nucleoli or sarcomatoid/spindled features

     

    Clinical

    • Frequently encountered lesions
      • 20-40% of kidneys at autopsy with increasing age
      • Increased frequency with end stage renal disease, especially with aquired cystic disease
      • Increased frequency in kidneys containing papillary carcinoma
    • Benign if strictly defined

    Classification / Lists

    Renal epithelial neoplasms

    Bibliography

    • Murphy WM, Grignon DJ, Perlman EJ. Tumors of the Kidney, Bladder and Related Urinary Structures, Atlas of Tumor Pathology, AFIP Fourth Series, Fascicle 1, 2004
    • Eble JN, Sauter G, Epstein JI, Sesterhenn IA eds. World Health Organization Classification of Tumors. Pathology and genetics of tumors of the Urinary System and Male Genital Organs. IARC Press: Lyon 2004.
    • Störkel S, Eble JN, Adlakha K, Amin M, Blute ML, Bostwick DG, Darson M, Delahunt B, Iczkowski K. Classification of renal cell carcinoma: Workgroup No. 1. Union Internationale Contre le Cancer (UICC) and the American Joint Committee on Cancer (AJCC). Cancer. 1997 Sep 1;80(5):987-9.
    • Kovacs G, Akhtar M, Beckwith BJ, Bugert P, Cooper CS, Delahunt B, Eble JN, Fleming S, Ljungberg B, Medeiros LJ, Moch H, Reuter VE, Ritz E, Roos G, Schmidt D, Srigley JR, Störkel S, van den Berg E, Zbar B. The Heidelberg classification of renal cell tumours. J Pathol. 1997 Oct;183(2):131-3.
    • Kovacs G, Fuzesi L, Emanual A, Kung HF. Cytogenetics of papillary renal cell tumors. Genes Chromosomes Cancer. 1991 Jul;3(4):249-55.
    • Wang KL, Weinrach DM, Luan C, Han M, Lin F, Teh BT, Yang XJ. Renal papillary adenoma--a putative precursor of papillary renal cell carcinoma. Hum Pathol. 2007 Feb;38(2):239-46.
    • Mallofré C, Almirall J, Campistol JM, Andreu J, Cardesa A, Revert L. Acquired a study of 82 nephrectomies in young patients. Clin Nephrol. 1992 Jun;37(6):297-302.
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