I understand your concern. BIRADS is a system of standardizing mammogram reports and the higher the number, the higher chances that the findings are indeed malignant. However, these should be differentiated or ascertained by a biopsy procedure as this is only the most dependable way to determine the exact nature of the lesions.
You can learn more about BIRADS through this website:
Regards and God bless.
OK, here goes .... the BIRAD 5 (and I'm speaking from personal experience) is highly suggestive of malignancy. The BIRAD 4 can very likely be something other than malignant .. a fair percentage of 4s are proven to be benign after biopsy. Just take things one step at a time and try not to panic about this ... the personal experience I referred to was 6 years ago and I'm fine. Best Wishes ..