Despite extensive development and testing, there is always a chance that a medication intended to treat a certain condition may contribute to the cause or progression of another condition. Such is the case for tamoxifen use in treating breast cancer, as a study has recently reported the first case of polypoid endometriosis to be associated with tamoxifen use in Korea.
“Polypoid endometriosis is one of the extremely rare benign complications associated with tamoxifen therapy,” stated the authors of the report, “Tamoxifen-associated Polypoid Endometriosis Mimicking an Ovarian Neoplasm,” which was published in Obstetrics & Gynecology Science. In polypoid endometriosis, women develop a polypoid tumor or mass that can be mistaken as cancer. Polypoid endometriosis itself is rare, with only three cases reported in the past in Korea, but polypoid endometriosis due to tamoxifen treatment seems to be even rarer.
Tamoxifen is commonly used as an adjuvant treatment for breast cancer. In the case at hand, a 66-year-old woman had breast cancer and received a partial mastectomy of the left breast. For the next four years, she was taking tamoxifen treatment but needed to stop due to an ovarian cyst. Upon pelvic sonography to visualize the pelvic cavity, it was revealed that the woman had multiple cysts on her right ovary. To clear up the cysts and endometriosis, she had a hysterectomy and bilateral salpingoophorectomy that removed both ovaries and their associated fallopian tubes.
When the clinicians treating the woman analyzed the polypoid mass, they noted “peripheral enhancement,” and determined the well-defined mass was likely a result of tamoxifen treatment. The final diagnosis was “an endometrial polyp with cervical endometriosis and paratubal polypoid endometriosis.”
One reason why tamoxifen may lead to polypoid endometriosis is that the compound can stimulate estrogen receptors on cells. Cells on the woman’s polypoid mass were positive for the estrogen receptor, so tamoxifen may have been stimulating the cells to grow into a mass. Knowing that polypoid endometriosis is a potential side effect of adjuvant tamoxifen treatment in breast cancer patients, clinicians may be advised to watch for this condition in their patients.