The occurrence of breast cancer metastasis in a uterine leiomyoma is exceptional, and its diagnosis prior to detection of the primary tumor is even rarer. We describe at case of a 52-year-old female patient with a large fast growing uterine fibroid that caused pelvic pain and abdominal distention. A total abdominal hysterectomy with bilateral salpingo-oophorectomy was performed. Histopathology of the surgical specimen showed a characteristic pattern of invasive breast lobular carcinoma in the leiomyoma.
A magnetic resonance image of the breast was then performed, which reveled primary and bilateral breast cancer. She subsequently underwent neoadjuvant endocrine therapy plus cyclin inhibitors, breast-conserving surgery, and radiotherapy. To date, the patient is alive and asymptomatic after 3 years of follow-up.