Tamoxifen therapy is well known for its success in adjuvant therapy for breast carcinoma; however, despite its benefits, the agents' estrogenic influence on the uterus, and subsequent endometrial cell proliferation may result in development of invasive uterine tumors. It has been estimated that tamoxifen may increase the risk of endometrial-based cancer two- to threefold, but uterine sarcomas remain relatively rare, accounting for 2 to 5 per cent of all uterine malignancies. We report the case of a 72-year-old woman having received tamoxifen for a breast carcinoma and having a hysterectomy nearly 30 years prior who presented with an intra-abdominal, omentum-based mass that on excision was identified as an endometrial stromal sarcoma.