A 69-year-old postmenopausal woman with newly diagnosed inflammatory breast cancer was evaluated for a pelvic mass found incidentally during staging computed tomography (CT) scans. Her serum cancer antigen (CA) 125 was greater than 900 U/ml, but laparoscopic examination of the ovaries was normal. Her breast cancer was deemed metastatic by virtue of a supraclavicular lymph node, but she had no visceral or bone metastasis. She was begun on primary chemotherapy and her CA 125 normalized. CA 125 is a tumor-associated antigen that is most commonly seen in advanced ovarian cancer. It is predominantly derived from coelomic epithelium, which explains elevations in benign conditions or other malignancies. The significance of CA 125 elevations in breast cancer is uncertain. Although CA 125 production has been demonstrated in the normal breast, it has been reported most often as a marker of pleural involvement with metastatic breast cancer. Further information on CA 125 in breast cancer is required to delineate its role in the management of this disease.