<p>Background: Lymphoedema of the arm may complicate breast cancer treatment, including sentinel lymph node biopsy, but when it is mild it is difficult to detect. This study considers the difficulties of diagnosing mild breast cancer-related lymphoedema particularly in relation to the natural differences between right and left arm volume.</p>n<p>Methods: Arm volume was measured opto-electronically in 33 women treated for unilateral breast cancer and in 37 age-matched healthy women. The ipsilateral arms of the breast cancer group were also examined closely for clinical signs of lymphoedema.</p>n<p>Results: On the basis of clinical examination, seven of the breast cancer group were found to have (previously undiagnosed) mild lymphoedema. The difference between ipsilateral and contralateral arm volume in three of these women was within the range of dominant minus non-dominant arm volume differences in the control group (and within 2 standard deviation [SD] of the mean difference). In the other four women, arm volume differences were outside the normal range (1–2 SD in one, greater than 2 SD in three).</p>n<p>Conclusions: Measurement of arm volume may not detect mild lymphoedema and close inspection of the arm is necessary. Early diagnosis and treatment are essential, as are detection and reporting for healthcare prioritisation.</p>n<p>Conflict of interest: None.</p>
