Before DCIS/LCIS, diagnosed with IDC today

If testing and treatment can be influenced by the individual oncologist, I think she/he might consider your relatively young age/premenopausal status as an argument for Oncotype testing if there is enough tissue, and for treating a little more aggressively — perhaps ovarian suppression plus aromatase inhibitor or tamoxifen, rather then just tamoxifen.

Barbara, your high ER and PR mean that it's unlikely that chemo will be recommended. With such a high ER and PR, your tumor should be very receptive to endocrine therapy which means chemo will likely provide little if any benefit.

As for what I meant when I said you are falling right on the line, from Ontario guidelines, take a look at these considerations of chemo:

• Lymph node positive: one or more lymph nodes with a macro-metastatic deposit (>2 mm)
• High-risk lymph node negative tumours with T size >5 mm and another high-risk feature (see next recommendation, R5)

Well, you are technically lymph node positive, but you have micromets not macromets. And your tumor is 4mm, just a bit smaller the >5mm cut-off (greater than 5mm could be as small as 5.1mm). The R5 list referenced in the second bullet mentions LVI as a factor that might indicate chemo with a >5mm tumor. You don't have lymphovascular invasion (or you haven't mentioned it) but you do have the micromets.

And here:

Patients with the following disease characteristics may not benefit from adjuvant chemotherapy:

• T <5 mm, lymph node negative and no other high-risk features (see R5)

You have a <5mm tumor but you aren't node-negative, so based on this, where do you stand? With a 4mm tumor that is node positive (but only micromets), you seem to fall in-between their "no chemo benefit" and "consider chemo" guidelines.

I completely understand your fear that you might have mets. That fear is normal - probably everyone diagnosed with invasive breast cancer gets hit with the same fear. So remember this - your diagnosis is more favorable than the vast majority of invasive cancer diagnoses. Tumors as small as 4mm aren't usually found - it's only because you had the DCIS that this tumor was found. And yes, you have the micromets, but a 0.3mm micromet is a hair width larger than a 0.2mm ITC (isolated tumor cells) and nodal ITC is actually considered node negative. Even micromets... in the past any nodal involvement automatically moved the staging to at least Stage II. But around 2011, a new Stage IB category was created specifically so that those with micromets could be moved into Stage I - because the research says that the prognosis is equivalent to Stage I. And in 2018, a second staging methodology came out, Pathological Prognostic Stage, which is used in addition to the traditional TNM (Tumor, Nodes, Metastasis) staging. Based on this new staging methodology, you are Stage IA. That's based on prognosis.

So yes, it's normal to be afraid that you might have mets. But the odds that you do are extremely small. Only 5%-6% of all breast cancer patients are diagnosed with Stage IV de novo (i.e. Stage IV at time of diagnosis) and I doubt there are many with a cancer as small and a diagnosis as favourable as yours.

I hope your MO appointment goes well and you are reassured by the discussion.