Key reasoning

1. A malignant tumour of the limb that can't be removed with limb salvage.
2. Uncontrollable infection or gangrene, such as necrotising infection or diabetic or ischaemic foot.
3. A limb that is useless or painful from a vascular or lymphatic cause.

Possible diagnoses

• RCC is a common kidney tumour in older men.
• It spreads to bone and soft tissue, and metastases to the limb can be large and destructive. The library includes a Campbell's Operative Orthopaedics section on metastatic carcinoma, with surgical treatment of bone and soft-tissue metastases from RCC (Campbell's Operative Orthopaedics 15th Ed 2026, Metastatic Carcinoma).
• RCC can also grow along the renal vein into the IVC as a tumour thrombus. That can cause leg swelling, but this is usually bilateral or involves the whole leg, not only below the knee.
• Left-sided involvement of the leg and a left renal mass would raise the question of left renal vein or iliac vein obstruction.

• A soft tissue sarcoma or bone sarcoma presents as a progressively enlarging leg mass, and amputation is a standard treatment when limb salvage isn't possible.
• Sarcomas mostly metastasise to the lungs (Bailey and Love's Short Practice of Surgery 28th Edition, Investigation). Kidney metastasis is uncommon.
• In an 82-year-old, undifferentiated pleomorphic sarcoma, liposarcoma and angiosarcoma are the usual candidates.

• This is angiosarcoma arising in chronic lymphoedema. It presents with bruise-like purple nodules in a long-standing swollen limb (Campbell's Operative Orthopaedics 15th Ed 2026, Malignant Vascular Tumors; Sabiston Textbook of Surgery, Radiation).
• It has a poor prognosis, and amputation is sometimes used.
• Ask about long-standing leg swelling, previous pelvic or groin surgery or radiotherapy, and purple skin lesions.

• It can cause leg swelling with purple plaques and nodules, and visceral involvement.
• It is linked to HHV8, HIV and immunosuppression (The Washington Manual of Medical Therapeutics, Epidemiology and Etiology).
• It is less likely at 82 unless he is immunosuppressed. The classic (Mediterranean) type does occur in elderly men.

• It can involve both the leg and the kidney. It is less likely to be treated with amputation.

• The kidney mass could be an incidental RCC or angiomyolipoma. The leg could have chronic infection, osteomyelitis, a non-healing ulcer with Marjolin ulcer (squamous cell carcinoma), vascular disease or diabetic foot.
• Chronic venous disease or lymphoedema with long-standing ulceration could be the problem, with the kidney mass found incidentally.

Syndromes I considered and think are unlikely

• Tuberous sclerosis and Von Hippel-Lindau disease: both involve kidney tumours, but they present much earlier in life.
• Klippel-Trenaunay syndrome and Proteus syndrome: both involve limb overgrowth, but they present in childhood.

What you need to find out

• How long has the leg been swollen, and did it start suddenly or gradually?
• Is it painful, and has there been weight loss, fever or night sweats?
• Is there haematuria or flank pain? That would suggest the renal tumour is symptomatic.
• Has he had previous cancer, radiotherapy, pelvic surgery or DVT?
• Does he have diabetes, peripheral arterial disease, smoking history, HIV or immunosuppression?
• Is there a history of trauma or a long-standing ulcer?

• Is the swelling pitting or non-pitting? Is it unilateral, and does it end at the knee?
• Look for a discrete mass, skin changes, purple nodules, ulcers, signs of infection and pulses.
• Check inguinal lymph nodes, abdominal masses and a left varicocele. A left varicocele can occur if a renal tumour blocks the left renal vein.

• Bloods: CBC, renal function, calcium, ALP, LDH, glucose and HbA1c.
• Imaging: MRI of the leg, plain X-ray of the leg, and CT of the chest, abdomen and pelvis. Doppler of the leg veins and arteries should also be done.
• Biopsy: a tissue diagnosis of the leg lesion and, if needed, the kidney lesion.

Summary