Define Renal Cell Carcinoma. Describe its clinical features and classification.

The Concept

Renal cell carcinoma (RCC) is an adenocarcinoma arising from the proximal renal tubular epithelium, and it is the commonest primary malignant tumour of the kidney in adults. It is sometimes called the 'internist's tumour' because it produces a remarkable variety of systemic and paraneoplastic features, and can present in many disguises — a point that makes it a favourite exam topic.

Risk Factors

The main risk factors are smoking, obesity, hypertension, and acquired cystic disease in patients on long-term dialysis. A hereditary form occurs in von Hippel-Lindau syndrome.

Clinical Features

• The classic triad — haematuria, loin pain and a loin mass — is actually a late finding present in only ~10%; nowadays most RCCs are found incidentally on imaging done for other reasons.
• Paraneoplastic features are characteristic: polycythaemia (erythropoietin), hypercalcaemia (PTH-related peptide), hypertension (renin), pyrexia of unknown origin, and Stauffer's syndrome (reversible hepatic dysfunction).
• A left-sided varicocele may occur when tumour invades the left renal vein and obstructs the testicular vein.
• Metastases classically produce 'cannonball' deposits in the lungs, and spread to bone.

Investigation & Management

CT is the key investigation for diagnosis and staging, showing an enhancing solid renal mass and assessing renal-vein/IVC involvement and metastases; ultrasound and blood tests support this. Management is chiefly surgical:

• Localised disease — radical or partial (nephron-sparing) nephrectomy.
• Metastatic disease — cytoreductive nephrectomy in selected patients plus targeted therapy (tyrosine kinase inhibitors such as sunitinib) and immunotherapy; RCC is notably resistant to conventional chemotherapy and radiotherapy.

Staging & the Role of the Renal Vein/ivc

RCC has a characteristic tendency to grow along the venous system, and this shapes staging and surgery. The tumour can extend as a tumour thrombus into the renal vein and up the inferior vena cava, occasionally reaching the right atrium — a feature that CT/MRI specifically assesses because it affects the operative approach. This venous behaviour also explains the left-sided varicocele (obstruction of the testicular vein) that can herald a left renal tumour.

WHY It Resists Chemo & the Rise of Targeted Therapy

A distinctive feature of RCC is its resistance to conventional chemotherapy and radiotherapy, which is why surgery dominates management. For metastatic disease, treatment has been transformed by targeted agents — tyrosine kinase inhibitors (sunitinib, pazopanib) acting on the VEGF angiogenesis pathway — and immune checkpoint inhibitors, reflecting the tumour's vascular and immunogenic biology (its link to the VHL gene and HIF pathway). Even in metastatic disease, cytoreductive nephrectomy may be beneficial in selected patients.

A Note on the Incidental Mass

Because so many RCCs are now found incidentally as a small enhancing renal mass on a scan done for another reason, an important modern issue is management of the small renal mass: options include partial (nephron-sparing) nephrectomy, ablation, or active surveillance in the elderly or unfit, since not every small mass is aggressive. This shift from the classic late 'triad' presentation to early incidental detection has improved outcomes.

A Note on the Bosniak Classification

In assessing renal masses, the Bosniak classification of cystic renal lesions on CT is a useful practical tool: it grades cysts from clearly benign (Bosniak I–II) through indeterminate (IIF, needing follow-up) to those with an increasing likelihood of malignancy (III–IV, warranting surgery). This helps decide which incidentally-found renal cystic lesions can be safely watched and which need intervention — an increasingly important judgement now that so many renal lesions are detected incidentally on imaging.

• Classic triad (haematuria + loin pain + loin mass) is late and present in only ~10%; most are incidental.
• Paraneoplastic: polycythaemia (EPO), hypercalcaemia (PTHrP), hypertension (renin); left varicocele (renal-vein invasion); cannonball lung metastases.
• Treat by radical/partial nephrectomy; metastatic → TKIs (sunitinib)/immunotherapy (resistant to chemo/radiotherapy).

Known as the internist tumour for its paraneoplastic syndromes.

• RCC = adenocarcinoma of proximal renal tubular epithelium; commonest adult renal cancer; 'internist's tumour' (paraneoplastic features).
• Risk: smoking, obesity, hypertension, dialysis/acquired cystic disease, von Hippel-Lindau.
• Classic triad (haematuria, loin pain, mass) is late/uncommon; most incidental; paraneoplastic (polycythaemia, hypercalcaemia), left varicocele, cannonball lung mets.
• CT for diagnosis and staging (enhancing renal mass, renal vein/IVC).
• Radical/partial nephrectomy; metastatic → TKIs (sunitinib)/immunotherapy (resistant to chemo/radiotherapy).