The oncological agent tamoxifen has pro-oestrogenic changes on the endometrium resulting in abnormal growth with an increased prevalence of:
- endometrial polyps: occurs in ~8-36% of women in treated 8
- endometrial hyperplasia: occurs in ~1-20% of women treated ref
- cystic endometrial atrophy
- endometrial carcinoma
Up to one-half of breast cancer patients who are treated with tamoxifen may develop an endometrial lesion within 6-36 months. Therefore, any patient who develops bleeding while taking tamoxifen requires evaluation.
Tamoxifen is a non-steroidal selective estrogen receptor modulator (SERM), which acts as an "anti-estrogen". It binds to the estrogen receptor and is used primarily for adjuvant therapy in breast cancer. However, it can also act as a pro-estrogen agonist in a low estradiol environment. The agonist properties can affect the endometrium, and does, in half of treated patients.
Tamoxifen may cause the endometrium to appear thickened, irregular, and cystic. Most patients tend to display a multiplicity of findings.
normal endometrial thickness despite tamoxifen use, i.e. <5 mm (although ~50% of those receiving tamoxifen have been reported to have a thickness of >8 mm) 2
- it has also been reported that the degree of endometrial thickening corresponds to the duration of tamoxifen therapy
- subendometrial cysts
- usually larger than in untreated women
- sonohysterography may be useful for their identification
Endometrial thickening and subendometrial cysts, similar to pelvic ultrasound.
Treatment and prognosis
Ultrasound screening of asymptomatic patients taking tamoxifen has been shown to be problematic due to a high number of false positives. It is thus not recommended routine ultrasound is performed for screening if a lady on tamoxifen is not experiencing bleeding.
It has been proposed that patients taking tamoxifen who present with vaginal bleeding should go directly to hysteroscopy and endometrial biopsy 7.
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