FALSE-NEGATIVE RATE IN INDENTIFYING AXILLARY NODE METASTASES

In one of the original Ludwig node-negative chemotherapy trials, there were 900 patients who later had enhanced pathology on their nodes (serial sectioning or more sections done with H&E staining), 10 to 15 percent of them actually had positive disease in those axillary lymph nodes. When we give our pathologists 20 lymph nodes, what usually happens is that maybe one or two slices are taken. Sometimes lymph nodes are missed completely; we ask them to go back and re-gross the specimen and they find six more lymph nodes. So, the false-negative rate is absolutely understandable.

When I give my pathologist one or two sentinel lymph nodes, they can afford to do serial sectioning or at least more sections through the node. And if they are negative on H&E staining, they can then afford to do immunohistochemistry. We’ve known that with small node-negative breast cancers, 10 to 15 percent will fail systemically. And now here we are 10 years later saying, “Gee, 10 to 15 percent weren’t node-negative. They were actually node-positive originally. ” So, one of the challenges is to find out whether the group that recurs systemically is the group that was misclassified as node-negative originally, and that work is going on right now.

—Patrick Borgen, MD

International (Ludwig) Breast Cancer Study Group. Prognostic importance of occult axillary lymph node micrometastases from breast cancers. Lancet 1990;335-1565. Abstract

DCIS & SENTINEL LYMPH NODE BIOPSY

We divide DCIS patients into high-risk and low-risk.High-risk winds up being about 30 percent of our cases — low--risk, 70 percent. We perform sentinel node mapping only in the high-risk group — defined as a breast filled with DCIS, (where you ’re doing a mastectomy) palpable DCIS or DCIS with a mass on mammogram. These would be patients in whom we would definitely perform a sentinel node biopsy. If we have H&E disease in the sentinel node and still no invasive carcinoma in the breast, that’s treated as N1 disease. At the other end of the spectrum, a single cell on IHC in a patient with DCIS, more often than not is not treated as N1 disease. These are taken on a case-by-case basis. Thankfully, we only get positive nodes in 10 percent of our high-risk DCIS population or three percent of our total DCIS population. So, dealing with IHC-only positive disease in a lymph node and DCIS is a very rare event — less than one in 100 cases.

Many people have argued that in DCIS, serially sectioning the breast is the best way to look for invasion.We argue that it’s not — that doing a sentinel node biopsy, looking for that metastatic cluster, is actually a better way to rule out invasion.

In the patient with an invasive carcinoma it’s a different story, because there, the majority of our patients, by virtue of having tumors greater than a centimeter, are destined to receive cytotoxic chemotherapy anyway. So, what we’re looking at is a small subset of patients with subcentimeter cancers, who have these cells in these lymph nodes. And again, thankfully, it’s a very small subset of our patients.

—Patrick Borgen, MD

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