renal oncocytoma

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Images

 macroscopy

• https://twitter.com/TheUSCAP/status/720607917737521152

Synopsis

 architecture : variable

• nested architecture / solid nests
• broad clusters
• tubular architecture
• glandular architecture / acinar architecture
• tubulocystic architecture

 tumoral stroma

• loose stroma
• Stroma may be extensively hyalinized in some cases of oncocytoma.
• Fresh hemorrhage within the lumina of tubulo-ductular structures as well as within the stroma is frequently seen in oncocytomas.
• Possible psammoma bodies / psammomas.
• The stroma in oncocytomas can sometimes show patchy calcifications , calcospherites , osseous metaplasia , and myeloid metaplasia

 uniform cells with regular round or oval nuclei.
 The nuclei are vesicular and show punctate nucleoli.

 possible focal nuclear atypia

• Focal atypia of degenerative type is quite common in oncocytomas.
• It consists of marked nuclear hyperchromasia and nuclear pleomorphism.
• However, there is no increase in mitotic activity and Ki-67 labeling index.
• Frequent sharp demarcation between zones of degenerative atypia and usual morphology.

 The cytoplasm is granular and eosinophilic.

• deeply esoinophilic granular cytoplasm
• eosinophilic tumor cells
• oncocytic tumors cells

 Focal papillary formations are sometimes seen protruding from the walls of larger cystic structures in oncocytomas.

• The papillae are rudimentary and lack fibrovascular cores.
• Prominent well-formed papillary structures are not seen.

 Focal extension into perinephric fat is seen in about 20% of renal oncocytomas.
 There is no desmoplastic response.
The presence of this feature does not impact pathologic staging.

 In less than 5% of cases, vascular invasion is seen.

• In an otherwise typical oncocytoma, this feature does not carry any clinical significance.

Immunochemistry

Positive IHC

 CD117+ (c-kit) (71%) (15105658)
 Low molecular weight cytokeratin (CK8 / 18, may be dot like)
 CK14 (strong)
 EMA
- Vimentin (focally positive in 73%)
 CD117 / c-kit (Am J Surg Pathol 2004;28:676)
 E-cadherin
 S100

Negative IHC

 CK7 (may have intensely positive scattered cells in a background of negative staining cells),
 CK20 (variable)
 CD10 (usually)
 Low Ki67 labeling index

Differential diagnosis

 eosinophilic variant of chromophobe renal cell carcinoma (chromophobe RCC)

• nuclear irregularities
• perinuclear haloes
• diffuse positivity for CK7

Predisposition

 Birt-Hogg-Dube syndrome (BHD)
 renal oncocytomatosis (renal oncocytosis)

Cytogenetics

 Chromosomal translocations involving the CCND1 locus at 11q13 (16337860) and overexpression of cyclin D1 occur in a subset of renal oncocytomas.

• Renal oncocytomas lacking cyclin D1 overexpression may be associated with the development of multiple renal oncocytomas and these patients are more likely to develop subsequent renal oncocytomas. (19386349)
• The data also show that cyclin D1 overexpression and CCND1 rearrangements by fluorescence in situ hybridization are absent in chromophobe renal cell carcinoma, suggesting that these are useful when differentiating between renal oncocytoma and chromophobe renal cell carcinoma. (19386349)

 ins(8;11) (multifocal transformation to chromophobe renal cell carcinoma) (16337860)

References

 CCND1 rearrangements and cyclin D1 overexpression in renal oncocytomas: frequency, clinicopathologic features, and utility in differentiation from chromophobe renal cell carcinoma. Sukov WR, Ketterling RP, Lager DJ, Carlson AW, Sinnwell JP, Chow GK, Jenkins RB, Cheville JC. Hum Pathol. 2009 Apr 20. PMID: 19386349

 Al-Saleem T, Cairns P, Dulaimi EA, Feder M, Testa JR, Uzzo RG. The genetics of renal oncocytosis: a possible model for neoplastic progression. Cancer Genet Cytogenet. 2004 Jul 1;152(1):23-8. PMID: 15193438