[alicem]

There are 2 types of tests that can be performed to determine your Her2 status. If they can retest your biopsy, perhaps they can do the IHC test the second time.

Testing methods

The two main methods used for HER2 testing are immunohistochemistry (IHC) and fluorescence in-situ hybridization (FISH):
Immunohistochemistry (IHC)

Immunohistochemistry (IHC) can show how much of the HER2 protein is present in the tumour sample. The HER2 level is graded from 0 to 3+.

• 0–1+ means that a normal amount of the HER2 protein is present and the result is HER2-negative
• 2+ means that a moderate amount of the HER2 protein is present
• 3+ means that there is a higher than normal level of HER2 protein and the result is HER2-positive.

When a tumour is scored at 2+, UK testing guidelines recommend that a further test is carried out. This is because a result of 2+ does not always mean a cancer cell has a high level of HER2. In this situation, an extra test (FISH) is used to give a definite result.
Fluorescence in-situ hybridization (FISH)

Whereas IHC measures the level of HER2 protein in the tumour sample, FISH testing measures the amount of the HER2/neu gene in each cell. This gene is responsible for the overproduction of the HER2 protein.
There is no number scale for FISH testing. The result is either:

• FISH-negative – normal levels of the gene are present, or
• FISH-positive – excessive amounts of the gene are present. This is sometimes called gene amplification.