IMMUNOHISTOCHEMISTRY, HER-2 / ERBB2

What this test checks

Measures the level of HER2 protein in breast cancer (or gastric cancer) tissue. HER2-positive cancers have an excess of this growth protein and respond to targeted drugs like trastuzumab (Herceptin).

Why do people get this test?

HER2 status completely changes breast cancer treatment. HER2-positive patients can receive highly effective targeted therapy (Herceptin) that significantly improves survival — but only if the cancer is correctly identified as HER2-positive.

When you should consider this test

• After diagnosis of breast cancer — as part of the standard ER/PR/HER2 receptor panel
• When planning treatment for HER2-targeted therapy
• For gastric or gastro-oesophageal junction cancer staging

How to prepare

No preparation needed — performed on biopsy or surgical tissue.