In my previous two posts on understanding your pathology report, we covered histology, margin status, grade, as well as size, lymph node status, Estrogen Receptor and Progesterone Receptor. Now I'll cover just a few more items to finish up our tour of the breast cancer pathology report, including HER2 Status, how fast the cancer is dividing, and "angio invasion" -- or invading blood vessels:
HER2 is the third receptor that is commonly looked for - a member of the EGFR family of receptors. A receptor is a place where a protein can sit and cause the cell to divide - in this case the HER2 receptor is on the cell membrane. Overexpression of HER2 is important to know because (1) it portends for a worse prognosis and (2) that prognosis is dramatically improved with adjuvant Herceptin, a targeted therapy to HER2.
In house pathology labs usually score HER2 as 0, 1+, 2+ or 3+. If a HER2 is 3+ it is considered positive. A confirmatory, more sensitive test, is called FISH which is usually sent to an outside lab. About 15% of HER2 0 or 1 will be HER2+ so these are not usually sent for FISH, but a 2+ is sometimes sent for FISH as many of these can be FISH positive, which in effect means HER2+.
With the recent news from San Antonio suggesting that "all HER2+ breast cancers require adjuvant chemotherapy and Herceptin" this assumes an even grater importance than before.
Ki67 or MIB, S Phase, Growth Fraction
These all measure a similar thing - that is how rapidly the cancer is dividing or what proportion of the cancer is actively dividing. The higher the number, the more aggressive the tumor. Different pathology facilities may use one or more of these measures - they correspond a little to grade, but have their own importance attached to them. Sometimes "high" "intermediate" or "low" may go along a number to represent this.
Even though the breast cancer may not show up in the lymph nodes the presence of lymphatic invasion - tumor crawling towards the lymph vessels - is concerning. Angio invasion - invading blood vessels - is also concerning as cancer can spread through the bloodstream in addition to the lymphatic system.
The future will look much different....and much better!