<p>Oedema of the upper limb may be attributable to several factors, including malignancy, venous or lymphatic abnormality. This article illustrates the concept of differential diagnosis for lymphoedema, by critically reviewing the diagnostic tests and examinations performed to investigate unilateral arm swelling in a 51-year-old woman. It reveals the pitfalls of using non-standardised diagnostic tests and suggests that evidence-based protocols for diagnostic procedures are necessary if we are to correctly diagnose the causes of oedema and provide patients with effective treatment for the condition.</p>
