Papillary Adenoma
Definition
- Benign renal cortical neoplasm with papillary/tubular pattern measuring ≤1.5 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 not have clear or chromophobe cells
- May be no larger than 1.5 cm
- Any larger lesion should be considered carcinoma
- Must be low grade cytologically
- WHO/ISUP nuclear grade 1 or 2
- Any higher grade lesion should be considered carcinoma
- Absent to inconspicuous nucleoli
- Stippled to clumped chromatin
- Mitotic figures very rare
- WHO/ISUP nuclear grade 1 or 2
- 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
- If numerous, consider adenomatosis
- May have an irregular interface with surrounding tissue
- No desmoplastic response
- May be multiple
- Must have only papillary or tubular architecture
- Lining cells usually
small with scant pale cytoplasm
- Similar to papillary carcinoma type 1
- Occasional cases with abundant eosinophilic cytoplasm
- Similar to papillary carcinoma type 2
- Psammoma bodies and foamy macrophages may be seen
- Similar changes in lining of Bowman capsule termed "adenomatoid metaplasia of Bowman capsule"
- A definitive diagnosis of adenoma is not recommended for needle biopxy specimens
- Partial encapsulation and nucular grade heterogeneity cannot be ruled out
Kurt Schaberg MD
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
Last revision November 1, 2016
