Why does a doctor order an MRI for breast cancer?

My mom had her first mammogram and the doctor found a 4cm non-fluid filled lump.  He had her go for a needle biopsy and while she was in her gown waiting for that, another nurse came in and said that she wasn't going to have that procedure after all.  The doctor had found something suspicious in her right breast and was ordering an MRI next week instead.  She went to the dr originally for tingling in her left arm and pain in her tailbone.  Waiting for an MRI next week, and then waiting for the results after that is going to feel like an awful long time.  Can someone give me an idea of what all the above might mean and also if it's normal for a doctor to order an MRI?  I appreciate your help...Lisa

[Fernando Roque, MD]

Hi.  A breast MRI is ordered to further clarify some suspicious findings seen in a mammogram or breast ultrasound.  The MRI offers superior resolution than mammography or ultrasound, and can detect smaller lesions.  But it is not done as the first screening procedure because of the cost.  It is standard procedure to order an MRI if findings in other imaging modalities are unclear.

[DrBhumikaMD]

Hi,
An MRi is done to confirm the mammogram and USG findings. Also an MRI would also pick up lesions in dense areas of the breast that a mammogram would have missed. An MRI is very sensitive but not done routinely due to the cost factor and hight rate of false positives.

[susied0828]

I had a positive mammo & ultrasound...also biposy which shows me a Triple Negative.....orders for MRI followed.......said to be done for staging and to decide lumpectomy or mastectomy...is this noral procedure?????

[japdip]

Yes,, it is quite routine to order an MRI since this is a much more sensitive type of imagery and is especially valuable when the breast tissue is very dense. In the future it would be better if you would post your question as a new one rather than as a comment connected to another question the way you did this time. We don't often go back and re-read comments; especially one that is associated with a question that is 2 years old. The MRI will give a much clearer picture of the suspicious area and be helpful in deciding the appropriate type of surgery. Kindest regards .....