Just Diagnosed with IDC

Twinsmama, this is the DCIS Forum.  DCIS is a different form of breast cancer from IDC.  So some of the issues you face with IDC may be different than that women with DCIS have.   To connect with other women who have a diagnosis similar to yours, you might want to post again in one of these forums on this discussion board:

IDC (Invasive Ductal Carcinoma)  

or

Just Diagnosed

or

Surgery - Before, During, and After

In the meantime, I can try to help with your question.  A pathology report from a biopsy won't have an estimated size of the area of cancer.  The estimate of the size comes from the imaging that's been done - the mammogram and/or ultrasound and/or MRI.  And it is just an estimate - there is no way to know the actual size until the surgery is done and all the suspicious tissue is examined under a microscope. 

After assessing the imaging, usually your surgeon will let you know how large he or she estimates the area of cancer to be.  As for what's too large an area of cancer for a lumpectomy, that depends on the size of your breast.  If your surgeon (or in this case, your oncologist) offers that a lumpectomy is a viable option for you, then have your answer.  Your doctors would not be talking with you about having a lumpectomy if they believed that the size of your cancer was too large for a lumpectomy to be an effective and reasonable option.