Dcis

It's a good question and it can be really confusing.  Here's how it works:

DCIS cancer cells are contained within the milk ducts.  The milk ducts hold the cells in place within the breast.  So DCIS cannot spread beyond the breast.  But there are two things that DCIS can do. 

• One is to spread within the ductal system of the breast.  This is why many of us are diagnosed with widespread areas of DCIS.  All the cancer cells are safely contained within the milk ducts, but much of the ductal system within the breast is affected.  This is the reason why a lot of women with DCIS require mastectomies - there's simply too much DCIS to remove with a lumpectomy.  
• The second thing that DCIS can do is become IDC.  As soon as a single cell of DCIS breaks through the wall of the milk duct and moves into the breast tissue, it is no longer DCIS.  Now this same cancer cell has become IDC, and this changes the diagnosis.  Once a patient has IDC, further invasion is a possibililty.  

This is why it's so important to catch and treat DCIS while it's all still DCIS.  If it's completely removed at that point, it's 100% curable.  But if it's not caught until after the cells have started to break through the ducts, the risks are higher.  And that's why even the tiniest amount of microinvasion changes one's staging from Stage 0 (DCIS) to Stage 1 (IDC).  This is really not well understood.  Many women believe, and may even be told by their doctors, that they are "DCIS Stage 0 with a microinvasion".   Then, if they're found to have invasion into the lymph nodes, they think it was the DCIS that caused the invasion.  But in fact they were never Stage 0.  Their diagnosis was not really "DCIS".  There is no such thing as Stage 0 with microinvasion.  What the actual diagnosis is is Stage 1 T1Mic (Stage 1 tumor, "mic" for microinvasion).  In my case, I had about 9cm of DCIS, only 1mm of IDC and I tend to think of myself as a DCIS patient, but I know that I'm actually Stage 1.

So the net of it is that DCIS cannot spread, but DCIS evolve to become IDC, and IDC can spread. 

Hope that helps!   

I was dianosed with Stage 11 infiltrating ductal carcinoma. Three weeks ago I had a segmentectomy and axillary note dissection. My surgeon informed me on a follow up visit that I need more surgery for additional axillary node dissection. In other words it has spread to my lymp nodes. Here's the problem. My Oncologist says I don't need more surgery I just need to start chemotherapy and radiation now. He says I don't need all the side effects of the surgery.  I called my surgeon and he informs me that surgery is the stanard procedure. I did make a third opinion appt. with another Oncologist but canceled it after doing some research on the internet. My surgeon will be calling me tomorrow regarding rescheduling my surgery. Does any one out there have any imput? I would appreciate any infomation you might have. Thanks.