welcome to HCM.
It appears that you don't have breast cancer
because if your mammogram
show some abnormality suggestive of cancer,you need to do biopsy
and receive srurery/radiotherapy /chemotherapy
not follow up.
Most probalbly they were talking about BIRADS classification No 4.
BIRADS is 'breast imaging reporting and data system', and was established by the American College of Radiology. BIRADS is used to classify mammogram finding into numerical catagory.
The BI-RADS assessment categories are:
5-highly suspicious of malignancy,
6-known biopsy with proven malignancy.
Since you had BIRADS 4 lesion, you are asked to follow up with mammogram again.Nothing to worry.