Dr. Yen is a surgical oncologist with clinical and research interests in breast cancer, endocrine tumors, and health services. She has studied multiple aspects of care related to the management of ductal carcinoma in situ of the breast and outcomes of patients who undergo surgery for medullary thyroid carcinoma and primary hyperparathyroidism. Her present research focuses on studying breast cancer quality of care, patterns of care, and the relationship of these patterns of care to outcomes of care through the analysis of administrative data, Medicare claims, and tumor registry data. Current projects include studying lymphedema incidence and risk factors among older breast cancer women (funded by a Career Development Award by the National Institutes of Health) and hormone therapy use in older breast cancer women.