Renal tumors

Benign Renal Tumors - The Good Guys

• Angiomyolipoma (AML)

  • Composed of blood vessels, smooth muscle, & fat.
  • Fat-density on CT is diagnostic.
  • Risk of spontaneous hemorrhage, especially if > 4 cm.

• Oncocytoma

  • Gross: Mahogany-brown tumor with a central stellate scar.
  • Histo: Large eosinophilic cells packed with mitochondria.
  • Often asymptomatic and found incidentally.

• Renal Papillary Adenoma

  • Most common benign renal tumor.
  • Defined as a papillary tumor ≤ 1.5 cm.

⭐ High-Yield: Multiple and bilateral angiomyolipomas are strongly associated with Tuberous Sclerosis (TSC).

Renal Cell Carcinoma - The Clear Culprit

• Origin: Arises from the epithelium of the proximal convoluted tubule (PCT).
• Risk Factors: Major risks include smoking and obesity. Also associated with hypertension, male gender, and acquired cystic kidney disease.
• Pathology & Genetics:
  • Clear Cell (75%): Most common subtype. Associated with deletion of the VHL tumor suppressor gene on chromosome 3p. Grossly appears as a golden-yellow mass due to high lipid and glycogen content.
• Clinical Features:
  • Classic Triad (uncommon, <10%): Flank pain, palpable mass, and hematuria.
  • Paraneoplastic Syndromes: 📌 PEAR: PTHrP (hypercalcemia), Erythropoietin (polycythemia), ACTH (Cushing's), Renin (hypertension).

⭐ Invasion Tendency: RCC is notorious for invading the renal vein and inferior vena cava (IVC). This can obstruct the left gonadal vein, leading to a varicocele that fails to decompress when supine.

• Diagnosis: Abdominal CT with contrast is the gold standard for diagnosis and staging.

RCC Genetics & Staging - Code & Climb

• Genetic Triggers

  • VHL gene (von Hippel-Lindau): Deletion on chromosome 3p. Most common cause of sporadic & hereditary clear cell RCC.
  • MET proto-oncogene: Activating mutation on chromosome 7. Associated with hereditary papillary RCC.
  • BHD gene: Mutations linked to chromophobe RCC & oncocytomas.

• Robson Staging

  • Stage I: Tumor confined to kidney, <7 cm.
  • Stage II: Tumor confined to kidney, >7 cm.
  • Stage III: Extends into renal vein, IVC, or adrenal gland.
  • Stage IV: Invades beyond Gerota's fascia or distant metastases.

⭐ The classic triad of hematuria, flank pain, and a palpable abdominal mass is seen in only ~10% of RCC patients.

Wilms & Urothelial Tumors - Kid & Pelvis Invaders

• Wilms Tumor (Nephroblastoma)

  • Most common pediatric renal tumor, typically ages 2-5.
  • Presents as a large, palpable, unilateral flank mass; may cause hypertension.
  • Histology: Triphasic (blastemal, stromal, epithelial).
  • Associated with WAGR, Denys-Drash, Beckwith-Wiedemann syndromes.
  • 📌 WAGR: Wilms, Aniridia, Genitourinary anomalies, Retardation (mental).

• Urothelial Carcinoma (Renal Pelvis)

  • Presents with painless hematuria.
  • Risk factors: Smoking, aniline dyes, cyclophosphamide.

⭐ Field defect: Urothelial carcinoma is often multifocal, with synchronous or metachronous tumors in the ureter or bladder.

• Renal cell carcinoma (RCC) is the most common renal malignancy in adults; classic triad is hematuria, flank pain, and a palpable mass.
• Clear cell is the most common RCC subtype, associated with VHL gene mutations on chromosome 3p.
• Wilms tumor (nephroblastoma) is the most common renal malignancy in children, linked to WT1/WT2 mutations.
• Angiomyolipoma is a benign tumor strongly associated with tuberous sclerosis.
• RCC frequently causes paraneoplastic syndromes, like polycythemia (↑EPO) and hypercalcemia (↑PTHrP).