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Tumours of the Kidney and Urinary Tract


Introduction

Two types of cancer arise from the renal parenchyma: renal cell carcinomas and nephroblastomas. Renal cell carcinomas (also known as renal adenocarcinomas and previously as hypernephromas ) are confined to adults. Nephroblastomas (Wilms tumours) are developmental in origin and present in infancy or early childhood (see Ch. 51 ). Occasional benign renal tumours occur, for example, oncocytoma, adenoma and angiomyolipoma ( Box 36.1 ).

BOX 36.1
Histological Classification of Adult Renal Tumours

  • A.

    Malignant

    • 1.

      Conventional clear cell carcinoma (70%–80%)

    • 2.

      Papillary or tubulopapillary renal carcinoma (10%–15%)

    • 3.

      Chromophobe renal carcinoma (5%)

    • 4.

      Collecting duct carcinoma (rare)

    • 5.

      Medullary carcinoma (rare)

  • B.

    Benign

    • 1.

      Oncocytoma

    • 2.

      Papillary or tubular adenoma

    • 3.

      Angiomyolipoma

Tumours of the transitional cell epithelium lining the urinary tract (urothelium) are very common. They may arise anywhere in the tract, including the renal pelvicalyceal system, the ureters, the bladder and occasionally the urethra. Pelvicalyceal tumours are uncommon. These urothelial carcinomas (UCs) , previously known as transitional cell carcinomas , occur exclusively in adults and most commonly in the bladder. Squamous cell carcinomas (SCCs) sometimes occur in the urinary tract and probably arise from metaplastic squamous epithelium, caused by chronic irritation from stones or schistosomiasis. SCCs also arise occasionally in squamous epithelium at the urethral meatus. Very rarely, an adenocarcinoma develops in the bladder from glandular epithelial remnants of the embryological urachus, or a sarcoma may develop from connective tissue elements.

Renal Cell Carcinoma

Pathology of Renal Cell Carcinoma

Renal cell carcinoma accounts for about 3% of adult malignancies and is twice as common in males as females. It rarely develops before puberty, but may occur at any age thereafter, with the peak incidence between 60 and 70 years. Renal cell carcinoma mainly occurs sporadically, but there are rare familial forms, such as von Hippel–Lindau disease. The only proven environmental risk factor is tobacco use.

The main types of renal cell carcinoma are clear cell, papillary and chromophobe. C lear cell carcinoma is the most common form and originates in renal tubules. They are well circumscribed; the cut surface is yellow (caused by lipid accumulation), often associated with haemorrhage or necrosis.

Renal cell carcinomas vary in grade of malignancy. Small isolated tumours are often found incidentally at autopsy. Tumours of less than 2 cm rarely display invasion or metastasis. Bilateral tumours are present in about 5%. Large tumours invade surrounding tissues and may metastasise to paraaortic lymph nodes. Advanced renal cell carcinoma characteristically extends into the lumen of the renal vein and into the inferior vena cava (‘tumour thrombus’— Fig. 36.1 ). Distant spread is typically to lung, liver and bone. Lung metastases are often typical discrete ‘cannonball secondaries’ (see Fig. 36.4 ). Isolated metastases occasionally develop in the brain, bone and elsewhere.

Fig. 36.1, Renal Cancer Staging.

Staging of Renal Cell Carcinoma

Stage I tumours are ≤7 cm and confined by the renal capsule; stage II tumours are ≥7 cm and still limited to the kidney; stage III tumours have renal vein or perinephric tissues involvement but remain confined by Gerota perinephric fascia, and may have regional nodal spread; stage IV tumours invade beyond Gerota fascia, have nodal spread and may have metastatic spread (see Fig. 36.1 ).

Clinical Features of Renal Cell Carcinoma

The classic presentation is with the triad of haematuria , a mass and flank pain ; although all three features only occur in about 15% of cases, one is present in 40% of patients (see Figs. 36.2 and 36.3 ). Commonly, diagnosis is made incidentally by discovering a tumour on ultrasonography or computed tomography (CT) scanning. Renal cell carcinomas often become large before diagnosis owing to their retroperitoneal position; tumours larger ≥7 cm have a 17% chance of having already metastasised. Common and uncommon presenting features of renal cell carcinoma are summarised in Box 36.2 .

BOX 36.2
Presenting Features of Renal Cell Carcinoma

Common Presentations

  • Visible (frank) haematuria

  • Non-visible (microscopic) haematuria often discovered incidentally

  • Loin pain

  • Renal mass

  • Incidental finding on imaging

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