Rapid Review·Cardiovascular
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PATHOLOGY
T3Take a glanceLymphatic Drainage & Lymphedema
Focus on
When lymph cannot drain, and the malignancy that follows years later.
Key takeaways
When lymph cannot drain
Normal function
lymphatics return interstitial fluid and filtered protein to the venous system, draining through the thoracic duct into the left subclavian vein.Why the swelling does not pit
obstruction traps protein-rich fluid, which is why the resulting swelling is non-pitting lymphedema rather than the pitting edema of a low-oncotic or high-hydrostatic state. Early on the skin is still soft and the edema pits; with time collagen is laid down and the skin turns firm, dry and thick, and the edema stops pitting.Causes
- Post-mastectomy, axillary node dissection, or radiation. The most common cause in the United States.
- Filariasis from Wuchereria bancrofti, causing elephantiasis. The most common cause worldwide.
- Congenital, i.e. Milroy disease, and Turner syndrome.
- Malignant nodal infiltration, and chronic inflammation such as recurrent cellulitis.
Treatment
weight loss, limb elevation, compression bandaging and physiotherapy to push lymph along. Diuretics are contraindicated: the fluid sits in the interstitium, so diuretics only drain the already-depleted intravascular space and tip the patient into prerenal failure.Chronic lymphedema markedly raises the risk of cutaneous ANGIOSARCOMA
known as Stewart-Treves syndrome, classically in a chronically swollen post-mastectomy arm.Chylothorax
thoracic duct injury producing milky, triglyceride-rich pleural fluid.| Feature | Lymphedema | Pitting edema |
|---|---|---|
| Fluid | Protein-rich | Protein-poor transudate |
| Character | Non-pitting | Pitting |
| Distribution | Often unilateral | Usually bilateral |
| Mechanism | Lymphatic obstruction | Raised hydrostatic or reduced oncotic pressure |
| Long-term risk | Cutaneous angiosarcoma (Stewart-Treves) | None specific |
Years after a mastectomy, a violaceous nodule appears on the chronically swollen arm. What is it?
Cutaneous angiosarcoma, i.e. Stewart-Treves syndrome, the malignancy chronic lymphedema breeds.
How it's tested
Chronic post-mastectomy lymphedema of the arm predisposes to cutaneous angiosarcoma, which is Stewart-Treves syndrome, and the stem gives a violaceous nodule appearing years after breast cancer surgery in a chronically swollen limb. The other discriminator worth carrying is that lymphedema is non-pitting because the trapped fluid is protein-rich, which separates it immediately from the pitting edema of heart failure or hypoalbuminemia.
Go deeper
First Aid 2026 — CV/Pathology (lymphedema) · B&B — Lymphatic system · Mehlman — HY Microbiology (Wuchereria bancrofti); angiosarcoma cross-refs the Vascular Tumors page
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