Question: My core biopsy showed DCIS and there was an area that the doctor said was “suspicious for microinvasion.” I had a mastectomy and sentinel node biopsy–large area of DCIS but no invasion, my node was negative. I’m worried about the “microinvasion” and that I could have invasive carcinoma somewhere.

Answer: I have seen this before so your situation is not out of the ordinary. Sometimes on a small biopsy with DCIS it can be difficult to “rule out” a small focus of invasive carcinoma.  Microinvasion means a focus of invasive carcinoma measuring less than 1 millimeter.  Sometimes there are studies a pathologist can do to prove there is microinvasion but because the area is so small the test often doesn’t help. That’s probably why your pathologist said “suspicious” because it wasn’t a clear-cut area of invasion.  It was then appropriate for you to have a sentinel lymph node biopsy. It’s good that your node was negative and that there was only DCIS left so I wouldn’t worry there is invasive carcinoma somewhere that wasn’t found. Some studies seem to show to patients with only microinvasion have a similar prognosis to patients with just DCIS. I would follow-up with a medical oncologist to discuss further options now that your surgery is done.