Improvement in local control with radiation therapy translates to a survival benefit in patients with breast cancer. The magnitude this benefit is proportional to the magnitude of the improvement in local control. Since the proportional reduction of local recurrence with the addition of radiation is relatively constant, it is important to determine the probability of local recurrence in order to guide therapy. There are a number of factors, including lymph node involvement, lymphovascular invasion, and size of the primary tumor that correlate with risk of local recurrence. There is very little data on the prognostic significance of malignant cells in seroma fluid after mastectomy or axillary dissection. We report a case of a woman with atypical cells in a persistent seroma following mastectomy for node negative infiltrating ductal carcinoma.