Pathology

Pathology/C/68

Tumors of kidney

腎腫瘍

1. Overview

  • Most frequent benign tumor = cortical papillary adenoma.
  • Most frequent malignant tumor in adults = renal cell carcinoma (RCC).
  • Most frequent malignant tumor in children = Wilms tumor (nephroblastoma).

2. Cortical Papillary Adenoma (Benign)

  • Arises from tubular epithelium: cuboidal cells, clear cytoplasm, regular nuclei.
  • Frequent neoplasm.
  • Small (< 5 cm), yellow-gray, well-demarcated, mostly in cortex.
  • Prognosis depends on size: tumors > 3 cm may metastasize.

3. Oncocytoma (Benign)

  • Benign tumor of collecting ducts (intercalated cells).
  • Eosinophilic granular cytoplasm + numerous mitochondria.
  • Macroscopic: central satellite (stellate) scar.

4. Renal Cell Carcinoma (RCC)

Overview

  • Derived from renal tubular epithelium.
  • 60–70 yr, men > women.
  • Risk factors: smoking (#1), HTN, obesity, dialysis-associated PKD.

Three Molecular Forms

A) Clear cell carcinoma (most common, ~70–80 %)

  • Cells with clear or granular cytoplasm.
  • Invasive: invades renal vein → IVC → right heart (tumor thrombus).
  • Most sporadic; some familial — Von Hippel-Lindau (VHL) syndrome:
    • Predisposes to multiple neoplasms, especially hemangioblastomas of cerebellum + retina.
    • 1st allele: VHL1 gene loss — t(3;6), t(3;8), t(3;11).
    • 2nd allele: somatic mutation → tumor suppressor loss.

B) Papillary renal cell carcinoma (~10–15 %)

  • Papillary growth pattern with fibrovascular cores.
  • Often multifocal + bilateral; appears at early stage.
  • MET proto-oncogene (chromosome 7) — tyrosine kinase receptor for hepatocyte GF.
  • Trisomy 7 + MET mutation → ↑ activity → papillary RCC.

C) Chromophobe renal cell carcinoma (~5 %)

  • Least common.
  • From intercalated cells of collecting ducts.
  • Dark cells with clear perinuclear halo.
  • Extreme hypodiploidy — multiple chromosome losses (1, 2, 6, 10, 13, 17, 21).
  • Good prognosis.

Clinical course of RCC

  • Classic triad: hematuria + palpable mass + costovertebral (flank) pain.
  • Called “mimics of medicine” — paraneoplastic syndromes:
    • Erythropoietin → polycythemia
    • PTH-related peptide → hypercalcemia + cystic bone lesions
    • ACTH → Cushing syndrome
    • Renin → hypertension
  • Metastases: lungs, bones, lymph nodes, liver, brain.
  • 5-yr survival: ~45 %.

5. Wilms Tumor (Nephroblastoma)

Overview

  • Most common primary kidney tumor in children (2–5 yr).

Associated syndromes (3 groups)

  1. WAGR syndrome — Wilms + Aniridia + Genitourinary anomalies + Retardation (mental).
  2. Denys-Drash syndrome (DDS) — Wilms + gonadal dysgenesis + renal failure (early).
    • Both WAGR & DDS: WT1 gene abnormality (chromosome 11p13, critical for renal/gonadal development).
  3. Beckwith-Wiedemann syndrome (BWS) — organomegaly + macroglossia + hemihypertrophy + omphalocele (WT2 region, 11p15).

Morphology

  • Large, solitary, well-circumscribed mass.
  • Can be unilateral or bilateral.
  • Microscopic: triphasic — attempts to recapitulate nephrogenesis:
    • Blastemal cells — sheets of small blue cells
    • Stromal cells — fibrocytic or myxoid
    • Epithelial cells — abortive tubules / glomeruli
  • 5 % have anaplasia — p53 mutations, chemo-resistant.

Clinical course

  • Palpable abdominal mass (often extending into pelvis).
  • Less common: fever, abdominal pain, hematuria, intestinal obstruction.
  • Tx: nephrectomy + chemotherapy → good prognosis (> 90 % cure).

6. Quick Comparison — RCC Subtypes

Subtype % Origin Key genetic Prognosis
Clear cell 70–80 % PCT VHL (3p) loss Variable; invades renal vein
Papillary 10–15 % PCT/DCT MET (7q), trisomy 7 Often multifocal/bilateral
Chromophobe ~5 % Collecting duct intercalated cells Multiple losses, hypodiploidy Best

💡 High-yield: Benign: papillary adenoma (<5 cm cortex), oncocytoma (collecting ducts, eosinophilic, central stellate scar). RCC = adult malignancy; smoking #1 risk; classic triad: hematuria + flank pain + palpable mass; paraneoplastic (EPO → polycythemia, PTHrP, ACTH, renin). Clear cell RCC = #1, VHL (3p), invades renal vein → IVC. Papillary = MET/trisomy 7, multifocal. Chromophobe = best prognosis. Wilms tumor = kids 2–5, WT1 (WAGR, Denys-Drash) / WT2 (Beckwith-Wiedemann), triphasic histology, palpable abdominal mass, excellent prognosis with nephrectomy + chemo.