Ectopic pregnancy in a breast cancer patient receiving trastuzumab.

Cervico-isthmic pregnancy is a rare form of ectopic pregnancy with a poor obstetrical prognosis, whose mechanism remains unclear. Preclinical data indicate that HER-2 plays a major role in embryo implantation. We report a case of cervico-isthmic pregnancy occurring during treatment with trastuzumab (Herceptin, a monoclonal antibody to HER-2). A 43-year-old woman presented with abnormal vaginal bleeding, while she was receiving trastuzumab for the last 14 months as an adjuvant therapy for a node-positive, HER-2 positive breast cancer. The diagnosis of evolutive cervico-isthmic pregnancy was confirmed by iterative ultrasonographic examinations. Given the poor obstetrical prognosis, the patient underwent voluntary abortion. The use of trastuzumab during pregnancy is still poorly documented, and its safety is not yet established. Given the importance of HER-2 in embryo implantation and fetal development, its putative role in this abnormal embryo implantation should be discussed.