Is Having MicroMetastases Considered A Positive Lymph Node?

Hi NClark6:

Is that correct that the amount of node involvement was 0.03 mm? Or did you mean 0.3 mm? Please confirm it against your pathology report to be sure.

Also, does your pathology report from lymph node biopsy include a nodal status? For example, does it include one of the following designations and a statement about use of AJCC staging criteria (with or without the "p")?

pN0(i+)

pN0(mol+)

pN1mi

BarredOwl

Hi Nclark6:

The short answer is that I believe pN1mi is considered node-positive.

Here is the definition of micrometastases from the 7th Edition of the AJCC Staging manual, per this summary document:

https://cancerstaging.org/references-tools/quickreferences/Documents/BreastMedium.pdf

pN1mi - Micrometastases (greater than 0.2 mm and/or more than 200 cells, but none greater than 2.0 mm)

Your question is whether the presence of a "micrometastasis" in one node would be considered "node positive". Staging is within the area of expertise of the pathologist, who designated the disease as pT1c, pN1mi(sn).

T1c is an indication of size and reflects the 1.9 cm (19 mm) size of the tumor, per page 1 of the chart above:

T1c Tumor > 10 mm but ≤ 20 mm in greatest dimension

(sn) - Per the chart above, "[c]lassification based solely on sentinel lymph node biopsy without subsequent axillary lymph node dissection is designated (sn) for "sentinel node," for example, pN0(sn)." Per a summary of changes in the 7th edition, "[u]se of the (sn) modifier has been clarified and restricted. When six or more sentinel nodes are identified on gross examination of pathology specimens the (sn) modifier should be omitted."

It is my layperson's understanding that any "pN1" status is considered node positive (as opposed to "N0"), although there are different degrees of positivity, per page 2 of the summary above:

pN1 - Micrometastases; or metastases in 1–3 axillary lymph nodes; and/or in internal mammary nodes with metastases detected by sentinel lymph node biopsy but not clinically detected***

pN1mi Micrometastases (greater than 0.2 mm and/or more than 200 cells, but none greater than 2.0 mm)

pN1a Metastases in 1–3 axillary lymph nodes, at least one metastasis greater than 2.0 mm

pN1b Metastases in internal mammary nodes with micrometastases or macrometastases detected by sentinel lymph node biopsy but not clinically detected***

pN1c Metastases in 1–3 axillary lymph nodes and in internal mammary lymph nodes with micrometastases or macrometastases detected by sentinel lymph node biopsy but not clinically detected

As further explained here:

http://annonc.oxfordjournals.org/content/24/11/2794.long

"Axillary nodes with ITC [isolated tumor cells] are considered to be cancer-negative and coded as pN0i+. Micrometastases are slightly larger with a diameter between 0.2 and 2.0 mm and are considered node positive and coded as pN1mi."

Your surgeon is correct that methods have evolved, and historically lesser amounts of involvement may not have been detected:

"As SLND has gained acceptance, efforts have been made to evaluate and report extent of disease within the axilla with greater precision. Extensive pathologic analysis has resulted in a complex system of nodal classification, including isolated tumor cells and micrometastases, which has generated significant debate as to the clinical relevance of small tumor deposits that likely would not have been identified in many cases in the era of routine axillary dissection. . ."

In another paper:

With the widespread use of SLND in patients with breast cancer and enhanced pathologic evaluation of SLNs, including serial sectioning and IHC, there has been an increase in detection of small-volume nodal metastases. To address this, the AJCC staging system was modified; first, small-volume metastases were designated as ITC [pN0(i+)] or micrometastases (pN1mi), and then T1 N1mi M0 disease was designated as stage IB."

Although your radiologist appears to be correct that "N1mi" is currently considered node-positive by pathologists, the pN1mi status was not the sole basis for the treatment recommendation you received. I note that under NCCN guidelines for breast cancer (Version 2.2016), the size of your ER - PR- HER2+ IDC (> 1cm) also lead to the recommendation for adjuvant chemotherapy plus trastuzumab. Had it been pN1mi, but less ≤ 0.5 cm, the guidelines say to "consider adjuvant chemotherapy with trastuzumab".

I am a layperson only, so if relevant to any treatment decision, patients should confirm any information above with the appropriate member of their treatment team.

BarredOwl