Treatment when clear margins are not found

I had a masectomy for DCIS which was found throughout my entire breast (although mammogram only showed a small calcification).  My pathology report said the DCIS went all the way out to the skin and therefore clear margins were not met there.  My surgeon says additional surgery could remove it.  I wanted to have the skin portion looked at by a pathologist while I was being operated on, but my surgeon said it wasn't necessary, but then how will I know the correct area of skin was removed?  Are there other treatments?  Do I have a strong possibility of breast cancer if left untreated?  Thank you.

[CCF-RN,MSN-JS]

Dear Frogger, Our breasts are made up of ducts, lobules, connective tissue and fat.  The function of the ducts is to bring milk from the lobules to the nipple when nursing a baby.   Ductal Carcinoma In Situ (DCIS) is confined within the lining of the ducts of the breasts.  It is an early cancer that has not become invasive (spread into the wall of the duct).   DCIS does have the ability over a long period to become invasive cancer if untreated, so these tumors have to be completely removed.  In your situation it sounds like DCIS was found in the different ductal systems throughout the breast.  If it was truly DCIS and not invasive cancer (the cancer invading the wall of the duct into the surrounding connective tissue or fat), then the only area where the skin would be involved is at the nipple, which is removed with the mastectomy.  If there was found to be a component of invasive cancer then the recommendation for any further treatment is based on the invasive cancer component.  

The short answer is; if the margins are positive or questionable a wider excision is recommended.