Breast Second Opinion if malignant or not

Good news.  The answer is NOT MALIGNANT.

The most significant finding is the atypical ductal hyperplasis.  ADH is a high risk condition but it's not cancer or even pre-cancer, although it does increase your breast cancer risk. I believe that someone with ADH has about a 20% - 30% lifetime risk, vs. about 12% for the 'average' woman. 

Did you have a core needle biopsy or an excisional (surgical) biopsy?  Usually when ADH is found in a needle biopsy, it is recommended that you have an excisional biopsy.  This is because in about 20% of cases where AHD is found, some cancer might also be lurking. Usually if this happens, the cancer is DCIS, which is a pre-invasive cancer and it the earliest stage of breast cancer.  80% of the time when an excisional biopsy is done after a needle biopsy finding of ADH, all that's found is more ADH. 

With ADH, you may want to enter a high risk screening program, or certainly you want to talk to your doctor about what your plan and schedule should be for future screenings. It might be recommended that you add ultrasounds and/or mammograms to your regular screening program.  I'd suggest that you check out the High Risk Forum in the Not Diagnosed but Concerned section on this board.  ADH comes up there a lot, and there is one particular thread that talks specifically about ADH:

Topic: ADH/ALH Are you doing anything different after diagnosis?