Tamoxifen-associated endometrial changes

The oncological agent Tamoxifentamoxifen has pro-oestrogenic effectschanges on the endometrium and thus is associated 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

Epidemiology

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. 

Pathology

Tamoxifen is a non-steroidal selective estrogen receptor modulator (SERM), which acts as an "anti-oestrogen" that. It binds to the oestrogen receptor and is used primarily for adjuvant therapy in breast cancer. However, it can also act as a pro-oestrogen agonist in a low oestradiol environment. The agonist properties can affect the endometrium, and does, in a high percentagehalf of treated patients (50%).

Radiographic features 

Ultrasound

Tamoxifen may cause the endometrium to appear thickened, irregular, and cystic.  Most Most patients tend to havedisplay 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
• endometrial polyps
  • usually larger than in untreated women 
  • sonohysterography may be useful for their identification

MRI

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 thusnot 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.