Background

50 year old male with incidental detection of mass in right kidney on ultrasound. Partial nephrectomy done thereafter.

Gross specimen

Fig. 17a; Gross: Well circumscribed tumor with mahogany brown cut surface and central scar

Microscopy

Fig 17b; H&E; 20x

Fig 17c; H&E; 20x

Immunohistochemistry

Fig 17d; CK7

Fig 17e; AMACR

Fig 17f; CD117

Fig 17g; SDHB

Fig 17h; E-Cadherin

Questions & Answers:

1. What is your diagnosis?
   • Oncocytoma
   • Chromophobe Renal Cell Carcinoma
   • Succinate Dehydrogenase deficient RCC
   • Low grade Oncocytic tumor
2. Which of the following is true for above tumor?
   • Strong CK7 and AMACR positivity
   • Subset of cases are CD117 negative
   • Positive for Hale colloidal iron staining
   • Negative for Low molecular weight cytokeratin
3. Hybrid case of Oncocytic tumor and Chromophobe RCC is seen in:
   • Birt-Hogg-Dube Syndrome
   • Tuberous Sclerosis
   • VHL syndrome
   • MIT Family translocation RCC

POINTS TO REMEMBER

• Oncocytoma is a benign epithelial tumor with solid, solid-nested, or cystic architecture
• Incidence: Constitute 5-9% of all renal cell neoplasm
• Age: Peak at 7th decade
• Clinical findings: Most of the cases are asymptomatic and are detected incidentally on radiological investigations for some other cause
• Location:
  • Predominantly cortex based
  • Large tumors can expand into medulla, renal sinus and even large renal vein branches
• Gross features:
  • Cut surface: Mahogany brown to tan or yellow with central scar
• Microscopic features:
  • Solid- nested architecture is characteristic
  • Rarely small papillary protrusion into renal tubules or in cystic areas
  • Composition of microcyst and macrocyst can occur
  • Some cases can show degenerative changes in the form of bizarre cells with pleomorphic nuclei
• Immunohistochemistry:
  • Positive stains: CD117, E-cadherin, Pancytokeratin & Low-molecular weight cytokeratin
  • Rarely positive for: CD10 & AMACR
  • Negative stains: CK7, Vimentin (may be positive in small cells around the central scar)
• Hale colloidal iron staining is negative but can show positivity in luminal aspect of cells
• Genetic susceptibility:
  • Sometimes can be seen in association with Birt-Hogg-Dube Syndrome: Have hybrid Oncocytic and Chromophobe tumor
• Differential Diagnosis:
  1. Chromophobe Renal cell carcinoma: Positive for CD117 & CK7, while are negative for Vimentin
  2. Low Grade Oncocytic tumor: Positive for CK7, while are negative for CD117
  3. Succinate dehydrogenase deficient RCC: Negative for CD117 & CK7. SDHB expression is lost

Contributed by: Dr. Meenakshi Kamboj

Compiled by: Dr. Diksha Karki

In case of queries, email us at: info.pathbliss@rgcirc.org

Kidney Neoplasms Oncocytoma Renal tumors

Last modified: 08/09/2021