Abstract Abstract #3103 Introduction: Lymphedema is well-known in the arm but can also occur in the breast. Diagnosis is currently non-standardized and based on clinical impression. We sought to determine if skin thickness could serve as a useful measure in the diagnosis of breast lymphedema (BLE).
 Methods: Patients undergoing unilateral non-mastectomy procedures were enrolled on this prospective clinical study preoperatively and evaluated for signs and symptoms of lymphedema in the operated breast in the postoperative period. Patients with established BLE were also studied. BLE diagnosis was independent of ultrasound findings and was based on a graded physical exam targeting clinical signs of edema and erythema. Skin thickness was measured with ultrasound at the 6 o'clock position of both breasts. Differences in skin thickness were assessed by the ratio of skin thickness in the operated and contralateral breasts, with comparison of means by two-sample t-test. Receiver operating characteristic curves were constructed to estimate the area under the curve (AUC) and to determine optimal cutpoints.
 Results: Ninety-seven women were studied; 85 were enrolled preoperatively and 12 postoperatively after a diagnosis of BLE. Median length of follow-up overall was 8 months. Of the 97 women, 46 had BLE at one or more follow-up visit with median time to first diagnosis of 3 months. Mean measured skin thickness was 2.3 ± 0.5mm in unaffected breasts and 3.2 ± 1.0 mm in operated breasts. Women with BLE had significantly greater skin thickness in the operated breast compared to the contralateral breast, with a mean skin thickness ratio of 1.83 ± 0.57 in patients with BLE compared to 1.18 ± 0.40 among those without BLE (p<0.0001). Skin thickness ratio provided excellent discrimination for BLE, with an area under the curve (AUC) of 0.86. At a ratio of 1.32 or greater (32% greater skin thickness in operated versus contralateral breast), sensitivity and specificity for diagnosing BLE were 81% and 82% respectively. A single measure of skin thickness in the operated breast also correlated well with diagnosis of BLE, with skin thickness of 3.2 mm or greater demonstrating sensitivity of 78% and specificity of 82%, AUC 0.82.
 Conclusions: Breast lymphedema results in skin edema and increased skin thickness that can be quantified with ultrasound. Measuring breast skin thickness- either as a single reading or as a ratio to the unaffected breast- may be useful in the diagnosis of breast lymphedema. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 3103.