Many women, young and old, have fibroid cysts on their breasts. It could very well be that. I wouldn't worry too much until you have your mammogram. Good luck and God Bless you.
The amount of echo transmitted from the sound waves of an ultrasound creates an image. In the case of hypoechoic masses, the image of the mass or lesion appears as increased density and is lighter when compared to the surrounding breast tissue. Typically, these masses are filled with fluid or air. And, they are often found to be benign in origin… so, the chance of malignancy is low. However, in order to determine the nature of the mass, a biopsy is usually recommended. The 4 o'clock indicates the location of the mass on the breast.