Abstract Background. Seroma formation or accumulation of serous fluid is one of the most common wound complications following breast cancer surgery, occurring from 30% as supported by needle aspiration to 85% as visualized on ultrasound in women following breast cancer surgery. It is postulated that seroma formation as a resultant collection of lymphatic fluid or acute inflammatory exudates is a response to surgical trauma and acute phase of wound healing. Seroma usually leads to prolonged wound healing, tissue inflammation and subsequent fibrosis and necrosis. It has been hypothesized that seroma formation is one of the main risk factors for post-breast cancer lymphedema. Lymphedema, exerts negative impact on breast cancer survivors’ quality of life. Understanding the relationship of seroma with lymphedema and related symptoms may help to reduce the risk of lymphedema through effective management of seroma. Purpose. To explore the relationship of seroma with lymphedema and related symptoms. Materials and Methods. Data were collected from 135 breast cancer survivors using a Demographic and Medical Information interview tool, clinical assessment, and Lymphedema and Breast Cancer Questionnaire for lymphedema related symptoms. Data analysis included descriptive statistics, t-tests, Chi-square, Fisher's exact test, and correlation coefficients. Discussion. Thirty-five patients (26%) developed symptomatic seroma following breast cancer surgery as evidenced by needle aspiration. Location of seroma formation included axilla, breast, and upper chest. Of the 35 women who had seroma, 33 (94%) of them demonstrated > 200 ml limb volume change determined onjectively by 4cm intervals. Clinical assessment based on International Criteria for Lymphedema Diagnosis revealed that 26 of the 35 women had severe lymphedema and the 6 patients had moderate while 3 had mild lymphedema. Age, type of surgery, number of lymph nodes removed and positive axillary lymph nodes were not correlated to seroma. Body mass index (BMI) was significantly correlated to seroma (r = .172, p = .04). Pearson correlations showed seroma formation was significantly correlated with symptom cluster of lymphedema (swelling, heaviness, firmness/tightness, numbness, and stiffness; r = .224, p = .009) and inflammation (redness, higher temperature, and tenderness; r = .287, p = .001). Significantly more women with seroma experienced a greater number of lymphedema related symptoms. Having seroma, lymph nodes removed and radiotherapy together accounted for 10% of lymphedema-related symptoms (R2 = .10, p = .003). Estimated relative risk for the women who had seroma in developing lymphedema was approximately 3 times more than those who did not (p = .00). Implications: It is important to assess and manage seroma formation. Evaluating symptom clusters of inflammation and lymphedema may be one of the cost-effective strategies to detect subclinical seroma to ensure timely interventions to prevent excessive fluid production and build-up. Current routine clinical management of symptomatic seroma is needle aspiration. Further research should focus on other effective strategies to minimize seroma formation, such as strategies of promoting fluid drain and prevention of inflammation. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P5-14-11.