Endometrial polyps are benign nodular outgrowths of the endometrial lining. They may be sessile or pedunculated. In the latter, the stalk, which usually contains a vascular pedicle, does not normally disrupt the endometrial lining. Histologically they are composed of stroma of dense fibrous or smooth muscle tissue, vessels, and endometrial glands.
Endometrial polyps are a common cause of vaginal bleeding in pre and post menopausal women. They can occur in 8-36% of patients treated with tamoxifen, due to the pro-estrogenic effects of tamoxifen on the endometrium.
Imaging findings of and endometrial polyp on transvaginal ultrasound are often non-specific, it is usually seen as a diffusely thickened and echogenic endometrium, rather than a focal mass within the endometrial cavity. Sonohysterosalpingography is better at characterizing polyps, where they are seen as intracavitatory well defined polypoidal lesions isoechoic to the endometrium, and outlined by the fluid.
The characteristic Pelvic MRI features of an endometrial polyp are that of a smoothly marginated intracavitatory mass that is hypo intense on T2, surrounded by hyper intense fluid, isointense to the endometrium on T1, and show homogenous or heterogenous contrast enhancement. Cystic areas may sometimes be seen within, due to the dilated endometrial glands.
Treatment is usually conservative. if the patients are symptomatic, then hysteroscopic resection is recommended. All resected polyps should be histologically examined to rule out malignant foci (0.5-3%).
The differential diagnosis includes:
- Uterine fibroid, especially if pedunculated and submucosal, though they are usually hypo echoic on ultrasound.
- Endometrial carcinoma, which is easy to distinguish when there are signs of myometrial invasion.