Thanks for your query,
Hypoechoic lesion at fundus is suggestive of a fibroid
. But the size of fibroid is not very significant. In case of your mother in law , she is suffering from post menopausal bleeding. In case of postmenopausal bleeding, investigations to rule out cancer is very much important. So you should not take it lightly, it may be serious occasionally.
So meet your OBG doctor earliest .
Best of luck and take care..
Hope it helps you..