Note that the polyp is sessile.

At transvaginal US, a submucosal fibroid may appear hypoechoic or show heterogeneous echogenicity and often demonstrate acoustic attenuation. The fibroid may displace or distort the endometrium or cause false endometrial thickening. At hysterosonography, a submucosal fibroid is seen as a round structure arising from the myometrium. The thin, overlying echogenic endometrium usually can be identified. It usually appears with a wide attachment to the myometrium but may be pedunculated.  

At transvaginal US polyps often shows nonspecific thickening of the central endometrial complex, with or without cystic changes. The presence of a distinct hyperechoic line partially or completely surrounding the abnormal endometrial complex favors a focal intracavitary process such as a polyp, a submucosal fibroid that protrudes into the cavity, or focal endometrial hyperplasia.

When a hyperechoic line is observed together with cystic spaces in the central endometrial complex, the focal mass is probably a polyp. Color Doppler US may show the feeding artery in the pedicle of the polyp, a helpful diagnostic feature. At hysterosonography, a polyp appears as an echogenic mass with smooth margins .Often it has a narrow attachment to the adjacent endometrium and is completely surrounded by fluid, although it could be broad-based. It often contains cystic areas but may have a homogeneous echotexture may also be seen at hysterosalpingography as pedunculated filling defects within the uterine cavity or at Color Doppler US may be used to image vessels within the stalk. Fibroids or foci of endometrial hyperplasia or carcinoma can mimic a sessile polyp, and foci of atypical hyperplasia are sometimes found within polyps.  

The MR imaging appearance of normal endometrium is best demonstrated on T2-weighted images because the uterus has homogeneous intermediate signal intensity with T1-weighted sequences. T2-weighted imagesdelineate the uterine zonal anatomy. The normal endometrium is of uniformly high signal intensity, and the inner myometrium, or junctional zone, is of uniformly low signal intensity.

At T1-weighted MR imaging, fibroids appear iso to hypointense relative to the myometrium, whereas at T2-weighted imaging they appear homogeneously hypointense or heterogeneously hyperintense when degeneration is present. Leiomyomas show increased signal intensity on T1-weighted images and lack of enhancement on postgadolinium images.

Polyps on T2-weighted MR imaging as low-signal-intensity intracavitary masses surrounded by high-signal-intensity fluid and endometrium.