Metastases of breast carcinoma to the uterus. Report of two cases, one harboring a primary endometrioid carcinoma, with review of the literature.

Background: Metastases to the uterus are rare, accounting for less than 10% of all cases of metastases to the female genital tract from extragenital cancers. The endometrium is even less frequently affected by metastases. Lobular carcinoma is the most common type of breast cancer that metastasizes to the uterus.

Cases: Two cases of infiltrating lobular carcinoma of the breast metastatic to endometrium and myometrium, one of them harboring an endometrioid adenocarcinoma, are reported. Both patients were on tamoxifen therapy and presented with uterine bleeding.

Conclusion: To the best of our knowledge, uterine carcinoma serving as recipient of metastatic carcinoma from the breast has not been previously documented. This possibility should be considered when an unusual bimorphic pattern appears in a tumor until proven otherwise.