Renal cell carcinoma 

• To help diagnose and manage simple and complex renal cysts, the Bosniak renal cyst classification system was created. 
• Based upon morphologic and enhancement characteristics with CT scanning, cystic renal masses are placed into one of five different categories
  • bosniak classification of renal cysts
    • Bosniak I
      • benign simple cyst
      • work-up: none
      • percentage malignant: ~0% 
    • Bosniak II
      • benign cyst – “minimally complex”
      • generally well marginated
      • work-up: none
      • percentage malignant: ~0%
    • Bosniak IIF
      • minimally complex
      • high-attenuation lesion >3 cm diameter, totally intrarenal (<25% of wall visible); no enhancement
      • requiring follow-up (F for follow-up): needs ultrasound/CT/MRI follow up – no strict rules on the time frame but reasonable at 6 months, 12 months, then annually for 5 years
      • percentage malignant: ~5%
    • Bosniak III
      • indeterminate cystic mass
      • thickened irregular or smooth walls or septa with measurable enhancement
      • treatment/work-up: partial nephrectomy or radiofrequency ablation in poor surgical candidates
      • percentage malignant: ~55%
    • Bosniak IV
      • clearly malignant cystic mass
      • Bosniak III criteria + enhancing soft tissue components adjacent to but independent of wall or septum
      • treatment: partial or total nephrectomy
      • percentage malignant: ~100%

• Simple renal cysts
  • Simple renal cysts are observed frequently in normal kidneys. 
  • They are the most common renal masses, accounting for roughly 65 to 70 percent of cases. 
  • The prevalence of simple renal cysts varies with the population studied and the imaging modality utilized. 
  • These cysts most often occur in patients over the age of 50. 
  • Simple cysts may be solitary, or multiple and bilateral. 
  • They typically produce no symptoms or signs. Rarely, however, they can be associated with rupture (hemorrhage), hematuria, pain, abdominal mass, infection, and/or hypertension. (See ‘Clinical features’ above.)
  • Simple renal cysts have characteristic changes on ultrasonography and computer tomography (CT). 
  • If basic ultrasonography criteria for a benign simple cyst are met, further study is not required. 
  • SUMMARY AND RECOMMENDATIONS
    • A renal lesion measuring <4 cm in largest dimension that demonstrates contrast enhancement on abdominal imaging meets criteria for a small renal mass.
    • The vast majority of small renal masses are renal cell carcinomas (RCCs). 
    • However, up to 30 percent of lesions <2 cm are benign.
    • Neither tumor size at diagnosis nor the growth rate is an accurate predictor of the presence of renal cell carcinoma. 
    • For patients with an incidentally detected small renal mass, we recommend a dedicated renal computed tomography (CT) or magnetic resonance imaging (MRI) as the first step in characterizing the lesion.
    • Percutaneous biopsy is indicated in patients with masses suspected to be a metastasis, focal infection, and in patients in whom surgery is not being contemplated
    • For patients with a small renal mass <1 cm in greatest dimension, we suggest active surveillance rather than surgical resection
    • For patients with a small renal mass ≥1 to 4 cm in size, who have a life expectancy >5 years, and are surgical candidates, we suggest surgical resection for a presumed RCC, rather than active surveillance or thermal ablation (Grade 2C).
    • For patients with a small renal mass ≥1 to 4 cm and are not surgical candidates, a biopsy should be performed. Patients with a biopsy proven RCC and those in whom an RCC cannot be ruled out are candidates for thermal ablation (Grade 2C). 
    • If thermal ablation is not an option, then patients should be offered active surveillance.
    • Patients with an uninformative result following a biopsy and those patients with a small renal mass who decline biopsy should be treated for presumed RCC.

Renal Cell Carcinoma

• Incidence – 50% more common in men than women , peak incidence at 64 (usually between 60-80 years of age)
• Clear cell RCC most common 75-85%, vs non clear cell (Papillary, chromophobe)
• Can also be TCC in renal pelvis
• Risk factors for RCC – Smoking, hypertension, CKD, obesity, PKD, previous radiation (ie childhood cancer survivors – should have regular screening apparently), von hippel landau
• Renal Cell Carcinoma treatment 
  • Localised treatment- Resection (radical of partial)
  • Metastatic – variety of treatments including IL-2, VGEF, mTOR inhibitos
• 5 year survival – 60 % overall (depends on stage obviously)