Renal Cell Carcinoma

Renal cell carcinoma (RCC) is the commonest primary malignant tumour of the kidney in adults, arising from the renal tubular epithelium. It is a favourite NEET PG topic that fuses surgical anatomy, oncology, paraneoplastic physiology and molecular genetics (VHL gene). Master the clear-cell predominance, the classical triad, IVC thrombus and the nephron-sparing vs radical nephrectomy decision.

Definition and Overview

RCC accounts for ~85–90% of all primary renal malignancies and ~2–3% of all adult cancers. It originates from the proximal renal tubular epithelium (clear cell and papillary types) or distal tubule/collecting duct (chromophobe, collecting duct types). It is classically a tumour of the 6th–7th decade, with a male preponderance (M:F ≈ 2:1). Synonyms you may see in old texts: hypernephroma and Grawitz tumour (based on the now-discarded belief that it arose from adrenal "rests").

High-yield: RCC is the kidney tumour notorious for being the "internist's tumour" because of its protean paraneoplastic and systemic presentations, and the "great mimic" because metastases can appear decades later.

Key risk factors

• Smoking (strongest modifiable risk; doubles risk).
• Obesity and hypertension.
• Acquired cystic kidney disease in patients on long-term dialysis (very strong association).
• von Hippel–Lindau (VHL) disease, tuberous sclerosis, Birt–Hogg–Dubé syndrome, hereditary papillary RCC.
• Phenacetin abuse, occupational cadmium/asbestos exposure.

Classification (Histological Subtypes)

The WHO classification is heavily tested. Learn the subtype, cell of origin, genetics and prognosis.

Subtype	Frequency	Cell of origin	Genetics	Prognosis / notes
Clear cell (conventional)	70–80%	Proximal tubule	VHL gene (3p25) loss	Most common; "golden-yellow" cut surface (high lipid/glycogen); most likely to form IVC thrombus
Papillary	10–15%	Proximal tubule	Trisomy 7, 17; MET mutation (type 1)	Often multifocal/bilateral; type 2 more aggressive
Chromophobe	5%	Distal tubule (intercalated cell)	Loss of multiple chromosomes; hypodiploidy	Best prognosis; perinuclear halo, "plant-cell" appearance
Collecting duct (Bellini)	<1%	Collecting duct	—	Very aggressive, young patients, poor prognosis
Medullary	rare	Calyceal epithelium	Loss of SMARCB1/INI1	Sickle cell trait patients; highly aggressive

High-yield: Clear cell RCC ↔ VHL/3p deletion. Chromophobe = best prognosis. Collecting duct (Bellini) and medullary = worst, aggressive. Renal medullary carcinoma classically affects young patients with sickle cell trait.

Etiology and Pathophysiology — the VHL Axis

The molecular story is the single most examinable concept.

Normal physiology: The VHL tumour-suppressor gene (chromosome 3p25) encodes pVHL, part of an E3 ubiquitin-ligase complex that degrades Hypoxia-Inducible Factor (HIF-1α/2α) under normoxia.

Pathogenesis flow: VHL inactivation (mutation/methylation) → pVHL cannot tag HIF for degradation → HIF accumulates → transcription of VEGF, PDGF, TGF-α, EPO → angiogenesis (hypervascular tumour), proliferation, and erythropoietin-driven polycythaemia.

This explains two exam pearls at once: RCC is a hypervascular tumour (basis for arterial enhancement on CT and the bleeding risk), and it produces erythropoietin (paraneoplastic polycythaemia). It also explains why anti-angiogenic tyrosine kinase inhibitors (TKIs) targeting VEGF are the backbone of systemic therapy.

High-yield: VHL loss → HIF accumulation → ↑VEGF and ↑EPO. This links the genetics, the hypervascularity, the polycythaemia and the choice of anti-VEGF drugs in one chain.

von Hippel–Lindau disease (the syndrome)

Autosomal dominant. Remember the constellation with the mnemonic "HARP" plus RCC:

• Haemangioblastomas (cerebellum, retina, spinal cord)
• Angiomatosis (retinal)
• Renal cell carcinoma (bilateral, multifocal, clear cell) and renal cysts
• Phaeochromocytoma; plus pancreatic cysts/neuroendocrine tumours and endolymphatic sac tumours

VHL-associated RCCs are bilateral, multifocal and present at a younger age — a classic reason to favour nephron-sparing surgery.

Clinical Features

Most RCCs today are incidentally detected on imaging done for other reasons ("incidentaloma"). The textbook presentation is late.

The classical triad

Flank pain + haematuria + palpable abdominal/flank mass.

• Occurs in only ~10–15% of patients.
• Its presence is a marker of advanced/locally extensive disease and poor prognosis — not an early sign.

High-yield: The classical triad (pain, haematuria, mass) appears in only ~10% and signifies advanced disease. The commonest presentation now is an asymptomatic incidental mass.

Local and metastatic features

• Haematuria (commonest single symptom; painless, gross).
• Left-sided varicocele that does not decompress on lying down → obstruction of the left testicular vein where it drains into the left renal vein (often by tumour thrombus). A non-reducing varicocele, especially right-sided, warrants imaging.
• Lower-limb oedema / Budd–Chiari / pulmonary embolism from IVC tumour thrombus.
• Metastases: lung ("cannonball" mets), bone (osteolytic), liver, brain, contralateral kidney.

Paraneoplastic syndromes (very high-yield)

Syndrome	Mediator	Clinical clue
Polycythaemia	Erythropoietin	↑Hb/Hct without hypoxia
Hypercalcaemia	PTHrP (and osteolytic mets)	Constipation, confusion, stones
Hypertension	Renin	New/refractory HTN
Stauffer syndrome	IL-6 (cytokine)	Reversible non-metastatic hepatic dysfunction — deranged LFTs/raised ALP with no liver mets, resolves after nephrectomy
Anaemia / cachexia	Chronic disease, cytokines	Most common overall systemic finding
Amyloidosis (AA)	Chronic inflammation	Proteinuria

High-yield: Stauffer syndrome = reversible hepatic dysfunction (raised ALP/transaminases, prolonged PT) without liver metastases, mediated by IL-6, reversing after tumour removal. A perennial favourite single-best-answer.

Mnemonic for paraneoplastic effects — "PRESH": Polycythaemia, Renin (HTN), Erythropoietin, Stauffer, Hypercalcaemia.

Diagnosis and Investigation of Choice

Approach: Incidental/symptomatic finding → ultrasound (first screening) → contrast-enhanced CT (CECT) abdomen — investigation of choice → stage chest (CT chest) → assess for IVC/renal vein thrombus (CT/MRI) → plan surgery. Biopsy is generally NOT done before nephrectomy for a classic enhancing solid renal mass.

• Ultrasound: Differentiates solid from cystic (Bosniak classification of cystic lesions). First-line, cheap.
• CECT (triphasic) — investigation of choice: A solid renal mass that enhances by >15–20 Hounsfield units after contrast is RCC until proven otherwise. CT also defines local extension, nodes, renal vein/IVC thrombus and the contralateral kidney.
• MRI: Best for defining cranial extent of IVC tumour thrombus (surgical planning) and in renal impairment/contrast allergy.
• Biopsy: Reserved for diagnostic uncertainty, suspected lymphoma/metastasis/abscess, or before ablation/systemic therapy — not routine for resectable solid masses (risk of seeding is small but enhancement is diagnostic enough).
• Bone scan/PET: Only if symptoms or raised ALP suggest bone disease; PET is not standard for primary staging.

High-yield: CECT is the investigation of choice for an RCC diagnosis and staging; MRI is superior for delineating the upper limit of IVC tumour thrombus. A renal mass enhancing >15–20 HU is RCC until proven otherwise.

Bosniak classification (cystic renal masses)

• I & II — benign, no follow-up.
• IIF — minimally complex, needs surveillance.
• III — indeterminate, ~50% malignant → surgery/excision.
• IV — clearly malignant (enhancing solid components) → surgery.

Staging (TNM / Robson)

The TNM system is preferred; Robson is older but still appears in questions.

Stage (TNM)	Definition
T1	≤7 cm, confined to kidney (T1a ≤4 cm, T1b 4–7 cm)
T2	>7 cm, confined to kidney
T3a	Invades perinephric fat / renal vein
T3b	Tumour thrombus in IVC below diaphragm
T3c	Tumour thrombus in IVC above diaphragm or invades IVC wall
T4	Invades beyond Gerota's fascia (incl. ipsilateral adrenal)

High-yield: Invasion beyond Gerota's fascia = T4. Renal vein/IVC thrombus is T3, not automatically incurable — an isolated IVC thrombus can still be resected for cure. Nuclear grade is given by the WHO/ISUP (formerly Fuhrman) grading.

Management and Drug of Choice

Surgery is the only curative modality. RCC is classically radio-resistant and chemo-resistant (due to MDR-1/P-glycoprotein expression) — so radiotherapy and conventional cytotoxics have little role except palliation.

Surgical decision flow

Localised mass → assess size, location, solitary kidney, bilaterality, baseline renal function →

1. Partial nephrectomy (nephron-sparing surgery, NSS) — standard of care for T1a (≤4 cm) and increasingly T1b; mandatory (imperative) for bilateral tumours, solitary kidney, VHL, or chronic kidney disease. Preserves nephrons → lower long-term CKD and cardiovascular mortality.
2. Radical nephrectomy — for T2 and large/central tumours; removes kidney within Gerota's fascia, with the perinephric fat. Ipsilateral adrenalectomy only if upper-pole/large tumour or adrenal involvement (not routine). Lymphadenectomy is for staging, not therapeutic.
3. IVC thrombus — aggressive surgery (sometimes with cardiopulmonary bypass for supra-diaphragmatic thrombus) can still be curative if no distant mets.

High-yield: Partial nephrectomy is the procedure of choice for T1a (<4 cm) RCC. Radical nephrectomy removes everything within Gerota's fascia. Routine ipsilateral adrenalectomy is not required.

Other local options

• Thermal ablation (radiofrequency/cryoablation) — small (<3–4 cm) tumours in elderly/comorbid/poor surgical candidates.
• Active surveillance — small renal masses (<2 cm) in frail patients.

Metastatic / advanced disease — systemic therapy

The therapeutic centrepiece reflects the VHL–VEGF biology.

• Cytoreductive nephrectomy in selected metastatic patients (good performance status).
• Tyrosine kinase inhibitors (anti-VEGF): sunitinib, pazopanib, axitinib, cabozantinib — historically first-line.
• mTOR inhibitors: temsirolimus (poor-risk), everolimus.
• Immune checkpoint inhibitors: nivolumab + ipilimumab, or pembrolizumab/nivolumab + axitinib combinations are now preferred first-line in many settings.
• Metastasectomy for solitary resectable mets.

High-yield: RCC is radio- and chemo-resistant. Metastatic RCC is treated with anti-VEGF TKIs (sunitinib/pazopanib), mTOR inhibitors (temsirolimus) and immunotherapy (nivolumab/ipilimumab) — directly exploiting the HIF/VEGF pathway.

Complications

• IVC tumour thrombus → pulmonary embolism, Budd–Chiari syndrome, lower-limb oedema.
• Paraneoplastic crises — hypercalcaemic crisis, refractory hypertension.
• Spontaneous tumour haemorrhage / Wunderlich syndrome (spontaneous perinephric haematoma).
• Late metastases — RCC is famous for relapse years to decades after nephrectomy; "cannonball" pulmonary metastases.
• Post-nephrectomy chronic kidney disease — the rationale behind nephron-sparing surgery.
• Erythrocytosis-related thrombosis from EPO secretion.

Key Differentials

Lesion	Distinguishing features
Angiomyolipoma (AML)	Contains fat (negative HU on CT); associated with tuberous sclerosis; benign
Oncocytoma	Benign; central stellate scar; "spoke-wheel" vessels on angiography; mahogany-brown; hard to distinguish pre-op
Transitional cell carcinoma (urothelial)	Arises from renal pelvis/calyces, filling defect on urography; risk factors smoking, analgesics
Wilms tumour (nephroblastoma)	Children; WT1 gene; abdominal mass in a child
Renal abscess / xanthogranulomatous pyelonephritis	Infective context, fever; "bear-paw" sign in XGP
Renal lymphoma / metastasis	Usually bilateral, history of primary; biopsy indicated
Simple/complex cyst	Bosniak I–II benign; IV malignant

High-yield: Macroscopic fat on CT = angiomyolipoma, not RCC. Central scar = oncocytoma. A renal pelvis filling defect points to TCC, not RCC. These are the classic "spot-the-difference" stems.

Recently asked / exam angle

• Single-best clue stems: "Painless haematuria + left varicocele not reducing on lying down + flank mass" → RCC with left renal vein involvement.
• Stauffer syndrome: deranged LFTs/ALP with normal liver imaging that reverse after nephrectomy — repeatedly tested.
• Paraneoplastic match: polycythaemia (EPO), hypercalcaemia (PTHrP), HTN (renin).
• Genetics: Clear cell RCC ↔ VHL gene, chromosome 3p. VHL disease triad (haemangioblastoma + phaeochromocytoma + RCC).
• Surgical anatomy: Radical nephrectomy removes tissue within Gerota's fascia; left testicular vein drains into the left renal vein (varicocele logic).
• Management MCQ: Procedure of choice for a 3 cm (T1a) tumour = partial/nephron-sparing nephrectomy.
• Subtype prognosis ranking: chromophobe (best) → clear cell/papillary → collecting duct/medullary (worst).
• Investigation of choice: CECT; MRI for IVC thrombus extent.
• Histology image: clear cytoplasm cells in a delicate vascular network (clear cell); perinuclear halos (chromophobe).
• Eponyms: Grawitz tumour, hypernephroma, Bellini duct carcinoma, Wunderlich syndrome.

Rapid revision

1. RCC = commonest adult primary renal malignancy; arises from proximal tubular epithelium; M > F, 6th–7th decade.
2. Clear cell = most common subtype (70–80%), linked to VHL gene loss on chromosome 3p25 → HIF/VEGF up-regulation.
3. Chromophobe has the best prognosis; collecting-duct (Bellini) and medullary (sickle cell trait) carry the worst.
4. Classical triad (flank pain + haematuria + mass) = only ~10%, indicates advanced disease; most are incidentalomas.
5. Left-sided non-reducing varicocele suggests left renal vein obstruction by tumour.
6. Paraneoplastic syndromes: polycythaemia (EPO), hypercalcaemia (PTHrP), HTN (renin), Stauffer (IL-6, reversible hepatic dysfunction without mets).
7. CECT is the investigation of choice; a renal mass enhancing >15–20 HU is RCC until proven otherwise; MRI best defines IVC thrombus extent.
8. T4 = beyond Gerota's fascia; T3 = renal vein/IVC thrombus (still potentially curable); grading by WHO/ISUP (Fuhrman).
9. Partial nephrectomy is the standard for T1a (<4 cm); radical nephrectomy (within Gerota's fascia) for larger tumours; routine adrenalectomy unnecessary.
10. RCC is radio-resistant and chemo-resistant; metastatic disease treated with anti-VEGF TKIs, mTOR inhibitors (temsirolimus) and immunotherapy (nivolumab/ipilimumab).
11. Differentials: fat on CT = angiomyolipoma, central scar = oncocytoma, pelvic filling defect = TCC, child = Wilms.
12. RCC is the cancer of late, unpredictable metastases; "cannonball" lung mets are characteristic.