DCIS - Sentinel Lymph Node (SLN) Positive?

I had ultrasound guided guided large core needle biopsy (USGLCNB) on 12/20/05. Path results: DCIS, high grade, solid, cribriform, comedo & neg for ER & PR. On 1/25/06, I had a WLE & SLN biopsy.  The WLE was the same type of DCIS. The entire WLE tissue was microscopically examined & NO  evidence of invasive carcinoma was identified. The SLN found, cytokeratin positive micrometastatic focus present in one of one nodes. In the cytokeratin stained section of the lymph node, there is a group of 6 to 7 cells forming two glandular structures which are located in the subcapsular sinus. These cells are not seen in the H&E stained sections, although they are present in the slide for the negative control of the immunohistochmical stain. Cytological features are pleomorphism, anistocytosis, & hyperchromatism.  Maximum size is .22 mm.  I had a bilateral MRI on which found an enhaced nodule in the axillary tail of the breast with the WLE. I had another USGLCNB: results were fragments of lymph node with no evidence of metastatic carcinoma. Treatment plan per surgeon: Radiation after re-excision for 1 close margin, have a clinical breast exam every 3 months and a mammogram once a year.  Per oncologist: No treatment needed.  The cells in the SLN are DCIS & were dislodged by the initial USGLCNB and therefore not invasive carcinoma.  She said my stage is 0 (T0, N0, M0)

How can the doctor tell form the path report that the cells in the SLN are indeed DCIS?
  
If they are DCIS, and more were dislodged, should I be concerned?  

Is a Her2neu test applicable for DCIS patients?

[CCF-RN,MSN-rf]

Dear Amaryliss:  By definition, ductal carcinoma in situ (DCIS) means that the cancer cells are within the duct and should not have the ability to spread.  The significance of microscopic lymph node involvement in the setting of DCIS is somewhat uncertain, however, the current staging system considers lymph node involvement to be present (N1) only if the size of the involvement is at least 0.2mm (more than just a few cells).  Expert review of the pathology to evaluate for any evidence of invasive cancer may be helpful. From the information you have provided, this may well be considered a stage 0 cancer, however, if you are uncomfortable with the recommendations, a second opinion may be helpful.