OBJECTIVE: The objectives of this study were to estimate ovarian malignancy rate in breast cancer patients with an adnexal mass and to identify variables predictive of malignancy. METHODS: This was a review from 1990-2002 including women with breast cancer diagnosed with an adnexal mass who subsequently underwent oophorectomy. Ovarian pathology was classified as benign, primary malignancy, or metastatic breast cancer. Women with preoperative evidence of malignancy were excluded. RESULTS: Of 129 cases reviewed, benign ovarian cysts were found in 113 cases (88%) and malignant ovarian neoplasms were found in 16 cases (12%). Univariate logistic regression analyses were performed to determine predictors of malignancy. Complex masses were 29 times more likely to be malignant (P < .001). Women with estrogen-receptor-negative breast cancer had an increased risk for malignant adnexal masses (44%; OR 12.4, 95%confidence interval 2.4-65.1; P = .003). Patients with an elevated CA-125 had a 6.3-fold increased risk of malignancy, P = .02. Adnexal mass size greater than 5 cm also increased the risk of malignancy (18.8%; OR 4.6, 95%confidence interval 1.2-17.3; P = .02). Malignant adnexal masses had a greater likelihood of being primary ovarian cancer than metastatic breast cancer by 7:1. CONCLUSION: An isolated adnexal mass in the breast cancer patient is most commonly a benign ovarian cyst. Adnexal masses associated with an increased CA-125, complex architecture by ultrasonography, or size greater than 5cm are significant predictors of malignancy and are indications for referral to a gynecologic oncologist. OBJECTIVE: The objectives of this study were to estimate ovarian malignancy rate in breast cancer patients with an adnexal mass and to identify variables predictive of malignancy. METHODS: This was a review from 1990-2002 including women with breast cancer diagnosed with an adnexal mass who Following underwent oophorectomy. Ovarian pathology was classified as benign, primary malignancy, or metastatic breast cancer. Women with preoperative evidence of malignancy were excluded. RESULTS: Of 129 cases reviewed, benign ovarian cysts were found in 113 cases (88%) and malignant ovarian Neoplasms were found in 16 cases (12%). Univariate logistic regression analyzes were performed to determine predictors of malignancy. Complex masses were 29 times more likely to be malignant (P <.001). Women with estrogen-receptor-negative breast cancer had an increased risk for malignant adnexal masses (44%; OR 12.4, 95% confidence interval 2.4-65.1; P = .003). Patients with an elevated CA-125 had a 6.3-fol d increased risk of malignancy, P = .02. Adnexal mass size greater than 5 cm also increased the risk of malignancy (18.8%; OR 4.6, 95% confidence interval 1.2-17.3; P = .02). Malignant adnexal masses had a greater likelihood of being primary ovarian cancer than metastatic breast cancer by 7: 1. CONCLUSION: An isolated adnexal mass in the breast cancer patient is most commonly a benign ovarian cyst. Adnexal masses associated with an increased CA-125, complex architecture by ultrasonography, or size greater than 5cm are significant predictors of malignancy and are indications for referral to a gynecologic oncologist.