A Simple Guide to the Different Ways HER2 Shows Up on Your Lab Report

Reading a lab report can feel like reading another language. If your non-small cell lung cancer report mentions HER2, you may see several different terms. HER2 (also called ERBB2) is a gene that helps control how cells grow. Keep reading to understand the main ways HER2 can appear on your report and the tests used to find each one.^1-4

The 3 main types of HER2 changes

HER2 can show up in lung cancer in 3 main ways. They are not the same, and they can happen on their own. They include:^1,4

• HER2 mutation – A change in the HER2 gene itself. The most common type in lung cancer is a small insertion in a part of the gene called exon 20. This can switch the receptor “on” so cells keep growing.
• HER2 amplification – Extra copies of the HER2 gene. More copies can lead to more HER2 signals telling cells to grow.
• HER2 overexpression – Extra HER2 protein on the surface of the cells. In lung cancer, this is measured by a stain and is not always caused by extra gene copies.
  Your report may mention one of these or more than one. Ask your doctor which type you have, since they can mean different things for treatment.⁴

Why the wording matters

The exact wording is important because approved targeted treatment is tied to a specific kind of HER2 mutation. For example, 1 targeted pill is approved for adults with advanced non-small cell lung cancer that has HER2 tyrosine kinase domain activating mutations, found by an FDA-authorized test. “Tyrosine kinase domain” simply names the part of the gene where the change is found.^1,2
Knowing whether your report says mutation, amplification, or protein change helps you and your doctor talk about the right next steps.

Tests used to find HER2 changes

Different tests look for different HER2 changes. Your report may list 1 or more of these:^1,3,4

• Next-generation sequencing (NGS) – Reads the DNA of the tumor and can find many changes at once, including HER2 mutations. It is the preferred way to find HER2 mutations when available.
• Fluorescence in situ hybridization (FISH) – Uses glowing markers to count copies of the HER2 gene. It is a long-trusted way to check for HER2 amplification.
• Immunohistochemistry (IHC) – Uses a stain to measure how much HER2 protein is on the cells.
• Liquid biopsy – A blood test that can find HER2 changes when a tissue sample is not available or is too small. Results may need to be confirmed with a tissue test.

What the numbers and scores mean

Some HER2 results come with a score. An IHC stain is often reported as 0, 1+, 2+, or 3+, which describes how much HER2 protein was seen on the cells. A higher score means more protein was found. Scoring for HER2 protein in lung cancer is not fully standardized, so results can vary between labs.⁴

For amplification, FISH results are based on the number of gene copies compared with a normal marker in the cell. Your report may include these details. The most useful step is to ask your doctor to walk you through your specific numbers.⁴

Questions to ask about your report

Bring these questions to your next visit:^1-4

• Which type of HER2 change do I have – a mutation, amplification, or protein change?
• What test found it, and was tissue or blood used?
• Do my results point to any targeted treatments or clinical trials?
• Should any result be confirmed with another test?

Talk to your doctor

A lab report is a starting point for a conversation, not the whole story. Ask for a copy of your report and have your doctor explain what each term means for you. Understanding your HER2 result helps you take an active role in your care.