Mom mammogram done and has been asked to come in for more images aday later. she has dense tissue in her earlier mammo. whats reason to call her again?

Possibly more tests: such as an Ultrasound of the breast or more angles in Mammography, There may have been an area of breast tissue that was needed to be defined in more detail. It may or may not lead to a biopsy.

Additional imaging: to further evaluate a potential abnormality, or an area not clearly visualized, occurs in about 10% of all screening mammograms(and probably at least 15% of baselines). 80% of the time it turns out to be nothing of concern. Of the remainder that go to biopsy, 80% of those turn out benign. So the odds favor a benign etiology, but in a small percentage of cases there is a cancer.