Renal Tumors - Summary Notes

Angiomyolipoma

  • Definition: An angiomyolipoma is a tumor, classified as a hamartoma, composed of blood vessels, smooth muscle, and fat.
  • Etymology: The prefix "angio-" refers to blood vessels, "myo-" to smooth muscle, and "lipo-" to fat.
  • Key Association: Increased frequency in patients with tuberous sclerosis, making it essential for exams.

Renal Cell Carcinoma (RCC)

  • Definition: Malignant epithelial tumor originating from kidney tubules.
  • Classic Presentation (Triad):
    • Hematuria: Blood in urine, the most common symptom.
    • Palpable Mass: Can be felt on examination.
    • Flank Pain: Pain in the side, though all three symptoms occur together in only 10% of cases.
  • Other Symptoms: May present with fever or weight loss.
Paraneoplastic Syndromes
  • RCC can produce multiple perineoplastic syndromes, which are symptoms or syndromes that occur due to the presence of cancer in the body:
    • Erythropoietin: Leads to reactive polycythemia.
    • Renin: Causes hypertension.
    • Parathyroid hormone-related peptide: Results in hypercalcemia.
    • ACTH: Causes Cushing syndrome.
  • Important: Awareness of paraneoplastic syndromes is high yield for exams.
Varicocele
  • Rare manifestation: A left-sided varicocele can occur due to RCC.
  • Anatomy Explanation:
    • The left spermatic vein drains into the renal vein, which may get obstructed by RCC invading the renal vein, hindering drainage and causing varicocele.
    • Right-sided varicocele is less common due to direct drainage into the inferior vena cava.
Histopathology
  • RCC typically presents a yellow mass; the most common histologic variant is the clear cell type, characterized by clear cytoplasm.
  • Genetics:
    • Loss of the VHL tumor suppressor gene is critical in RCC pathogenesis, leading to overexpression of growth factors like insulin-like growth factor (IGF), vascular endothelial growth factor (VEGF), and platelet-derived growth factor (PDGF), promoting tumor growth and angiogenesis.
Pathways to Development
  • Sporadic Pathway:
    • Single tumor, generally in the upper pole of the kidney, associated with adult smokers.
  • Hereditary Pathway:
    • Multiple, bilateral tumors, typically in younger patients.
    • Example of Hereditary Syndrome: Von Hippel-Lindau disease, an autosomal dominant disorder characterized by VHL gene inactivation, leading to increased risk of RCC and hemangioblastoma of the cerebellum.
Staging
  • RCC staging is based on tumor size and involvement of the renal vein, which relates to risks of hematogenous spread to the lungs and bones.
  • Lymphatic spread typically involves retroperitoneal lymph nodes.

Wilms Tumor

  • Definition: The most common renal tumor in children, average age of presentation is three years old.
  • Key Characteristics:
    • Composed of blastema, which is the primitive tissue indicative of kidney formation.
    • Blastema can also produce primitive glomeruli and stromal cells.
  • Presentation: Patients usually have a large unilateral flank mass, with both hematuria and hypertension (due to renin secretion).
Genetic Associations
  • Associated with WT1 mutations, particularly in syndromic cases.
  • High Yield Syndromic Examples:
    • WAGR Syndrome: Wilms tumor (W), aniridia (A), genital anomalies (G), mental and motor retardation (R).
    • Beckwith-Wiedemann Syndrome: Associated with Wilms tumor, presenting with neonatal hypoglycemia, muscular hemihypertrophy, and organomegaly (especially of the tongue).