Kidney

• In terms of coding rules, similar to lung
  Bilateral site with mixed functional tissues; would be helpful to have straightforward rules that are easy to use and understand
• Laterality
  Hard to determine whether one primary with metastases to contralateral lung or simultaneous multiple primaries
• Kidney and renal pelvis not functionally related
  Traditionally, the kidney and renal pelvis were grouped together as a single organ. However, the kidney develops glandular carcinomas (adenocarcinoma and renal cell carcinoma), while the rest of the urinary system, beginning at the renal pelvis develops transitional and squamous cell malignancies. Kidney should really be separated from the rest of the urinary tract because it has different functions, different histologies, and a different disease process.
• Histology coding is fairly simple
  a limited range of codes, predominantly renal cell carcinomas; however, some of the specific histology codes have lower numbers than the nonspecific histology code. When should the specific histology or a mixed histology code be used versus the nonspecific code?