MRI biopsy vs Digital Mammography

More than 8 weeks ago, my gynecologist saw some dimpling on my right areola.  My mammogram had been clear.  An ultrasound showed nothing but the gyno insisted I see a surgeon.  Surgeon had a breast MRI done and a small nodule was found.  Surgeon decided to do an MRI-guided biopsy.  After 2-3 weeks of cancelled biopsy appointments (insurance company is unable to do it in network), surgeon and insurance have decided to do a digital mammogram with possible biopsy.
I'm 56 and post-menopausal.  
Is this digital mammogram as reliable as an MRI?  What happens if the digital mammography doesn't find the problem?  Apart from stressing me out, will all this delay matter if there is a malignancy?

[BusyMommy]

Hi -

Wondering how this turned out.  Did you get an explanation for your dimpling?