Renal Tumors Overview

  • Defining Renal Tumors
    • Involves cancers originating from the kidney, including tumors in the renal pelvis and ureter.

Anatomy of the Kidney

  • Kidney Structure
    • Composed of renal pyramids, renal pelvis, and ureters.
  • Function
    • Excretes waste products from blood, regulates blood pressure, and helps maintain electrolyte balance.

Renal Cysts

  • Prevalence
    • Occurs in approximately 10% of the population.
  • Risk Factors
    • Increasing age, male gender, and worsening renal function.
  • Types
    • May be sporadic or genetic (e.g., Autosomal Dominant Polycystic Kidney Disease - ADPKD, Acquired Cystic Kidney Disease - ACKD).
  • Bosniak Classification of Renal Cysts:
    • Category I: Uncomplicated benign cysts with thin walls; no septations or calcifications; sharp delineation with renal parenchyma; no enhancement (risk of malignancy <1%).
    • Category II: Mildly complex cysts; thin walls with few (1-3) septa <2mm (risk of malignancy <3%).
    • Category IIF: More suspicious cysts with one or more septa or many (<4) septa <2mm; follow-up recommended.
    • Category III: More complicated cysts with thick, irregular septa (>4mm); risk of malignancy 5-10%; requires US/CT follow-up.
    • Category IV: Malignant cysts with enhancing nodules; surgical excision required (>80% risk).

Benign Tumors

  • Prevalence
    • Approximately 20% of suspected renal masses are benign, particularly if small.
  • Symptoms
    • Mostly asymptomatic; may become symptomatic when large.
  • Diagnosis
    • Ultrasound (US), CT with contrast, MRI; Pathology is definitive but typically post-surgery or via biopsy.
  • Management
    • Follow-up or surgery when symptomatic.

Types of Benign Tumors:

  • Adenoma

    • Small well-circumscribed cortical lesion.
    • Types include:
    • Papillary Adenoma: Premalignant to papillary renal cell carcinoma (RCC), typically <0.5 cm.
    • Metanephric Adenoma: Rare, can grow large, associated with case reports.
    • Cystic Nephroma: Common in young boys (ages 2-3), must be distinguished from Wilms tumor.

  • Oncocytoma

    • Most common benign tumor characterized by eosinophilic cells; only 20% cause symptoms like hematuria or flank pain.
    • Visualization techniques (US, CT) can resemble RCC; T99 sestamibi scan positive due to high mitochondrial density.
    • Treatment mirrors RCC: tumor resection/nephrectomy required.

  • Angiomyolipoma

    • A hamartoma consisting of dysmorphic blood vessels, smooth muscle, and adipose tissue.
    • Spontaneous rupture risk in 25% leads to retroperitoneal hematoma; pregnancy is a risk factor.
    • Diagnosis via CT, showing fat density (-20 to -80 HU) for confirmation.
    • Treatment includes follow-up, embolization, or nephrectomy.
    • Associated with Tuberous Sclerosis (55-99% will experience early presentation).

Renal Cell Carcinoma (RCC)

  • Statistics

    • RCC accounts for 90-95% of all primary malignant kidney tumors; represents 2-3% of all cancers in adults, with around 30,000 annual cases in the U.S.
    • 40% mortality rate among diagnosed patients.
    • Most commonly diagnosed in individuals aged 60-70 years; male to female ratio 2:1.

  • Etiology

    • Strongly associated with smoking, hypertension, and exposure to certain chemicals (shoe workers, leather tanners, cadmium, petroleum products).
    • Genetic factors: von Hippel-Lindau disease, chromosomal aberrations, and acquired cystic disease in patients on hemodialysis.

  • Pathogenesis

    • Characterized by direct invasion of surrounding tissues, including the renal capsule, perinephric fat, and adjacent organs, with a tendency to metastasize to lymph nodes, lungs, liver, bones, adrenal glands, and contralateral kidneys.

  • Pathologic Types

    • Clear Cell Type: 70-80%, poor prognosis.
    • Papillary Type: 10-20%
    • Type I: Good prognosis.
    • Type II: More aggressive.
    • Chromophobe Type: <5%, best prognosis.
    • Collecting Duct Carcinoma: Poor prognosis, <5% incidences.
    • Others include renal medullary carcinoma and sarcomatoid variants.

Genetic Considerations

  • Von Hippel-Lindau Disease

    • Autosomal dominant tumor suppressor gene mutation/inactivation; manifests with clear cell RCC.
    • Associated with significant multi-system presentations (e.g., retinal angiomas, hemangioblastomas).

  • Hereditary Papillary RCC

    • Autosomal dominant; tanslocations involving chromosomes 7 & 17; associated with less aggressive type 1 papillary RCC.

  • Hereditary Leiomyomatosis and RCC

    • Mutation of a tumor suppressor gene leading to Type 2 solitary, aggressive RCC.

Diagnosis of RCC

  • Clinical Presentation

    • Around 60% of patients are asymptomatic.
    • Common symptoms include hematuria (40%), flank pain (40%), and occasionally a palpable abdominal mass (25%).
    • Other signs of advanced disease: weight loss, fever, poor performance status.

  • Laboratory Work-Up

    • Key studies include:
    • Urinalysis
    • Complete Blood Count (CBC) with differential
    • Electrolytes, renal profile, liver function tests (AST, ALT)
    • Calcium levels
    • Erythrocyte sedimentation rate
    • Prothrombin time.

Imaging Studies

  • Ultrasound (US) and Intravenous Urography (IVU)

    • Findings: hypoechoic / isoechoic lesions with high vascularity are suggestive.

  • CT and Angiography

    • Effective for assessing renal masses and potential metastasis.

TNM Staging of RCC

  • T Classification:

    • TX: Primary tumor cannot be assessed.
    • T0: No evidence of primary tumor.
    • T1a: Tumor ≤ 4.0 cm confined to the kidney.
    • T1b: Tumor > 4.0 cm and ≤7.0 cm, confined to the kidney.
    • T2a: Tumor > 7.0 cm and ≤10.0 cm, confined to the kidney.
    • T2b: Tumor > 10.0 cm, confined to the kidney.
    • T3: Tumor extends into the renal vein or pericaval area, or invades surrounding structures but not beyond Gerota's fascia.
    • T4: Tumor invades beyond Gerota’s fascia.

  • N Classification (Regional lymph nodes):

    • NX: Regional lymph nodes cannot be assessed.
    • N0: No regional lymph node metastasis.
    • N1: Metastasis in regional lymph nodes.

  • M Classification (Distant Metastasis):

    • MX: Distant metastasis cannot be assessed.
    • M0: No distant metastasis.
    • M1: Distant metastasis present.

Staging of RCC

  • Stage I: Tumors < 7 cm, no regional lymph node involvement (N0), no distant metastasis (M0).
  • Stage II: Tumors ≥ 7 cm, again with no nodal or distant involvement.
  • Stage III: Tumors with nodal involvement but no distant spread (e.g., T1/T2 + N1 or T3 with any N).
  • Stage IV: Tumors with distant metastasis or significant local spread.

Treatment of RCC

  • Surgical Therapy:

    • Radical Nephrectomy
    • Indicated for large tumors (> 4 cm) in patients with healthy contralateral kidneys (GFR > 45).
    • Techniques:
    • Early control of renal vessels, removal of perirenal fat, and possible adrenalectomy.
    • Partial Nephrectomy: Recommended for tumors < 4 cm; considered for patients with solitary or functioning kidneys.

  • Cytoreductive Nephrectomy:

    • Offered to patients with metastatic disease to alleviate symptoms or before immunotherapy.

  • Thermal Ablation:

    • Cryoablation is an alternate for small tumors (T1a <3 cm) with low morbidity.

Management of Metastatic RCC

  • Immunotherapy:
    • Use of Interleukin-2 (IL-2) and Interferons, although associated with severe side effects.
  • Targeted Therapy:
    • Includes Tyrosine Kinase Inhibitors (e.g., sunitinib, sorafenib) and mTor inhibitors (e.g., tacrolimus, everolimus).
    • Immune checkpoint inhibitors (e.g., pembrolizumab, nivolumab).
    • Stereotactic Body Radiation Therapy (SBRT) is also utilized.

Upper Tract Tumors

  • Renal Pelvis Tumors:
    • Symptoms: Hematuria, renal colic, side pain.
    • Diagnosis:
    • Imaging techniques such as ultrasonography, CT, IVU, or cystoscopy.
  • Transitional Cell Carcinoma (TCC):
    • Urothelial carcinoma arising from the renal pelvis; most common but rare, representing 5-6% of all urothelial tumors.
  • Men are twice as susceptible; peak incidences occur at ages 60-70.
  • Diagnostic methods include CT and ureteroscopy, achieving 80-90% diagnostic accuracy.

Treatment of Renal Pelvis Tumors

  • Surgical Options:
    • Ureteroscopic coagulation with laser; radical nephro-ureterectomy is the main choice, often combined with bladder cuff excision.
    • Possible adjunctive treatments include radiation and chemotherapy post-surgery.