The exact pathogenesis of renal oncocytoma is not completely understood. Although some mechanisms are suggested in the pathogenesis of this disease that include, lossing of chromosome 1 and dysfunction of mitochondrial enzymes which is caused by alterations in the mitochondrial DNA. DNA diploidy is seen in 96% of patients with renal oncocytomas. The development of renal oncocytoma is the result of multiple genetic mutations such as deletion of chromosome 1, deletion of the sex chromosome, translocation of chromosome 11q13, sporadic or no chromosomal alteration. Renal oncocytoma can be associated with familial renal oncocytoma or Birt-Hogg-Dube syndrome. On gross pathology, tan to brown surface color , well-encapsulated with a thick, well-defined, fibrous capsule, central scar, and homogeneous appearance without any hemorrhage or necrosis inside it in the tumor cut are characteristic findings of renal oncocytoma. On microscopic histopathological analysis, renal oncocytoma characterized by “oncocytes”. They are large, round to polygonal neoplastic cells accompanied by eosinophilic granular cytoplasm and are organized in nested or organoid pattern. Although, renal oncocytoma is benign, atypia, prominent nucleoli, and pleomorphism may seen in microscopic examination.

• The exact pathogenesis of renal oncocytoma is not completely understood.
• The mechanisms which are suggested in the pathogenesis of renal oncocytoma include:^[1][2][3][4]
  • Lossing of chromosome 1
  • Dysfunction of mitochondrial enzymes which is caused by alterations in the mitochondrial DNA

DNA diploidy is seen in 96% of patients with renal oncocytomas.^[5][6][7]

The development of renal oncocytoma is the result of multiple genetic mutations such as:^{[8][9][10][1][2][11]}

• Deletion of chromosome 1
• Deletion of the sex chromosome
• Translocation of chromosome 11q13
• Sporadic or no chromosomal alteration

Conditions associated with renal oncocytoma include:^[12][13]

• Familial renal oncocytoma
• Birt-Hogg-Dube syndrome

Note: Birt-Hogg-Dube syndrome is an autosomal dominant syndrome which is presented with different types of dermatologic diseases and renal epithelial tumors such as renal oncocytoma and RCCs.

On gross pathology, tan to brown surface color , well-encapsulated with a thick, well-defined, fibrous capsule, central scar, and homogeneous appearance without any hemorrhage or necrosis inside it in the tumor cut are characteristic findings of renal oncocytoma.^{[14][15][16][17][18][19]}

On microscopic histopathological analysis, renal oncocytoma characterized by “oncocytes”. They are large, round to polygonal neoplastic cells accompanied by eosinophilic granular cytoplasm and are organized in nested or organoid pattern. Although, renal oncocytoma is benign, atypia, prominent nucleoli, and pleomorphism may seen in microscopic examination.^{[20][21][22][23][24]}