Lobular carcinoma of the breast metastasizing to leiomyoma in a patient under letrozole treatment.

Metastasis of extragenital neoplasms to the uterus is extremely rare. Lobular breast cancers metastasize to the uterus more than ductal carcinomas, but they metastasize as tiny nodules that can be missed with the standard diagnostic workup. Uterine involvement by a metastatic tumor is usually a manifestation of end-stage disease; patients are reported to die within weeks to months. Therefore surgery is not recommended. Here we report a case of lobular breast cancer metastasizing to a leiomyoma in a patient using letrozole. Our patient was submitted to surgery because the leiomyoma had grown to the level of the xiphoid process. She is alive one year after the operation. In conclusion growth of leiomyomas under aromatase inhibitors should be considered as a sign of metastases and surgery can be planned in selected cases.