DCIS - had bilateral mastectomy - Herceptin?

HI - I am 42. I was diagnosed with high grade DCIS, comedo-type, grade 3, with necrosis in my left breast December.  I was ER (greater than 75%) and PR (greater than 40%) positive. HER-2 was not tested (I since requested it be, and this is in the process). I had a bilateral mastectomy and Sentinel Node Biopsy (in January), and have delayed reconstruction (DIEP scheduled for April). My lymph nodes were negative. Mastectomy pathology report indicated my right breast (aka healthy breast) had numerous 'fibrocystic changes', adenosis and ductal hyperlasia, and several areas of fibrous stroma, but no malignancy.

My concern is that my mom also had medullary breast cancer (at age 40). This was in 1969. Her 'treatment' was single radical mastectomy, and she took weekly testosterone injections for 17 years! Can you also explain this treatment? I am assuming that since she was given testosterone, it likely had some indication that her cancer was estrogen driven, as well. She had a total hysterectomy a few years after the cancer, as well. My mom's sister also had (and died from breast cancer). My mom (and I) both had BRCA testing, both were negative.

I have researched a lot of websites, and it seems that there are lots of women with similar diagnoses as myself. After the mastectomies I think there are a lot of both 'guilt' for not having to have chemo (or radiation), and also a lot of 'worry' that we are just being dropped. I realize that by taking the aggressive approach of bilateral mastectomy, that in and of itself was a treatment. My oncologist, applauded my decision for the bilateral after looking at the pathology report.  

Now, for my final question... If I am HER-2 positive, would I benefit from Herceptin treatment? I just have a foreboding feeling that this may come back somewhere - in lingering breast tissue, skin, chest wall, etc. I cannot find an answer to this anywhere. I know my cancer wasn't invasive, but still it was breast cancer, and Grade 3. Thank you!

[Cleveland Clinic]

Dear Cimiche:  HER-2 is not routinely evaluated in DCIS.  In several studies, HER-2 was overexpressed in DCIS (especially high grade) with greater frequency that those with invasive cancer.  The clinical significance of this finding is not known. Since DCIS should not have the ability to metastasize, chemotherapy and trastuzumab would not be indicated (unless invasive cancer were present as well).  In estrogen/progesterone receptor positive DCIS, endocrine therapy such as tamoxifen is often recommended following breast conserving surgery in order to reduce local recurrence risk. Typically, no further treatment is recommended following mastectomy for DCIS.  We cannot speculate on the testosterone treatment that your mother received, however, in 1969 ER and PR testing was unlikely to have routinely been done. Incidentally, true medullary cancers of the breast are usually negative for ER, PR and HER2neu.