Her2/neu By FISH

Function

HER2 (Human Epidermal Growth Factor Receptor 2) by Fluorescence In Situ Hybridization (FISH) is a molecular test used to determine the amplification of the HER2 gene. In certain cancers, particularly breast and gastric cancers, the HER2 gene is over-replicated, leading to an overabundance of the HER2 protein on the cell surface. This protein signals the cells to grow and divide uncontrollably. While Immunohistochemistry (IHC) measures the protein, FISH measures the actual number of gene copies, making it the 'gold standard' for precision.

Why it is Ordered

This test is critical for oncology treatment planning. It is ordered for:

• All newly diagnosed invasive breast cancers.
• Recurrent or metastatic breast cancer cases.
• Advanced or metastatic gastric or gastroesophageal junction adenocarcinomas.
• Clarifying 'equivocal' (IHC 2+) results from immunohistochemistry tests.

Associated Conditions

The primary focus is HER2-positive Breast Cancer and HER2-positive Gastric Cancer. HER2-positive tumors tend to be more aggressive and grow faster than HER2-negative tumors. However, the identification of HER2 amplification is a significant clinical opportunity because these cancers respond exceptionally well to targeted therapies such as Trastuzumab (Herceptin), Pertuzumab, and T-DM1. Determining HER2 status is a prerequisite for prescribing these life-saving HER2-targeted agents, which have drastically improved the prognosis for patients who would otherwise have a poor outlook.