Question: I have been diagnosed with invasive ductal carcinoma. The biopsy results said the tumor was ER and PR positive, and HER2 negative, and a grade 2. However, after surgery, the pathology report said ER positive, PR negative, and didn’t mention the HER2 status at all. It also changed the grade down to a 1. The tumor was 1.7 cm. How can the pathology be different from the biopsy? And which one should I consider as being correct? Can the grade of a tumor change? Thanks for your help.

Answer: Yes, this can happen because a core biopsy is a much smaller sample, so on a surgical excision the pathologist has the entire cancer to evaluate. Most studies have shown a very good (but not perfect) correlation between grade and hormone receptor status/HER2 between core biopsy and surgical excision. I would likely trust the surgical excision results because there is more of the tumor to evaluate–and I wouldn’t worry too much about the PR changing–what’s more important is that the ER is still positive which is a good thing! I don’t know why they would repeat the ER/PR but not the HER2 unless it was a different laboratory that processed your surgical excision and they do not perform HER2 testing given the new regulations. If this didn’t answer your question, please email me back.