Human epidermal growth factor receptor 2 positive status

This code indicates the presence of an overexpression or amplification of the HER2 gene in a patient's tumor cells. This genetic alteration is a significant biomarker, particularly in breast and gastric cancers, influencing prognosis and treatment decisions. It signifies that the cancer cells have an increased number of HER2 receptors, which can promote cell growth and division.

Use this code when laboratory testing, such as immunohistochemistry (IHC) or fluorescence in situ hybridization (FISH), confirms HER2 positivity in a tumor. This is commonly identified during the diagnostic workup for breast cancer, gastric cancer, or other malignancies where HER2 status is clinically relevant. It is crucial for guiding targeted therapies.

• Assign this code as a secondary diagnosis to the primary malignancy code.
• Ensure documentation clearly states "HER2 positive" or "HER2 amplified" based on pathology reports.
• Do not use this code if HER2 status is negative or equivocal; specific codes exist for those findings.