Surgical Pathology Criteria

Renal Oncocytoma

Differential Diagnosis

Chromophobe Renal Cell Carcinoma Renal Oncocytoma
Diffuse, sheet like pattern Nests floating in hypocellular stroma
Perinuclear halos usually prominent No perinuclear clearing
Clear cells usually prominent, frequently peripheral in nests Clear cells only focally in hyalinized scars
CK7 usually diffuse, strong CK7 usually negative or scattered positive cells
Hale colloidal iron stain diffusely positive Hale colloidal iron stain may be apical, but not diffuse, confluent

Conventional Clear Cell Renal Cell Carcinoma, Granular Variant Renal Oncocytoma
Nearly always has clear cell areas Clear cells only in focal, hyalinized scar areas
Prominent surrounding capillary network Surrounding stroma hypocellular
Carbonic anhydrase IX, AMACR/racemase, vimentin usually pos Carbonic anhydrase IX, AMACR/racemase, vimentin usually neg
cKIT/CD117 usually neg cKIT/CD117 usually pos

Renal Oncocytoma Oncocytic Papillary Renal Cell Carcinoma
Solid, with minimal, poorly developed papillary change Usually predominantly papillary
At most, rare, focal foamy macrophages May have clusters of foamy macrophages
Necrosis is rare and only microscopic foci May have tumor cell necrosis
AMACR/racemase/P504S usually negative AMACR/racemase/P504S positive
Occasional oncocytic papillary renal cell carcinomas may be largely solid; the bottom three criteria are more important in such cases

Tubulocystic Carcinoma of the Kidney Renal Oncocytoma with Cystic Features
Overwhelmingly cystic Usually solid nests with focal cystic dilation
Fibrotic stroma Loose hypocellular stroma
Large irregular nuclei Large round nuclei
Consistent prominent nucleoli Nucleoli variably present
Racemase and CD10 positive Racemase and CD10 usually negative

Renal Oncocytoma Neuroblastoma Associated Renal Cell Carcinoma
No history of neuroblastoma History of neuroblastoma
Rare in children Most in children, some in young adults
Minimal papillary component Usually papillary
Neuroblastoma associated carcinomas are typically composed of oncocytic cells, which may pose this differential

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