Human epidermal growth factor receptor 2 negative status

This code indicates that a patient's tumor cells do not overexpress the human epidermal growth factor receptor 2 (HER2) protein. This status is determined through laboratory testing, typically immunohistochemistry (IHC) or fluorescence in situ hybridization (FISH), and is a crucial biomarker in cancer management.

Use this code when documentation explicitly states a HER2-negative status, particularly in breast cancer or gastric/gastroesophageal junction adenocarcinoma. It is often reported following biopsy or surgical resection results to guide treatment decisions.

• Always ensure the medical record clearly documents the HER2-negative status based on laboratory findings.
• This code is typically used as a secondary diagnosis, accompanying the primary malignancy code.
• Do not use this code if the HER2 status is unknown, equivocal, or positive.