HER2positiva

HER2-positiva describes tumors that overexpress the human epidermal growth factor receptor 2 (HER2) due to amplification of the ERBB2 gene. In breast cancer, HER2-positive tumors comprise about 15–20% of cases and are typically more aggressive than HER2-negative tumors. HER2 overexpression can also occur in gastric and gastroesophageal junction cancers and, less commonly, in other tumor types.

Diagnosis is based on tumor testing. Immunohistochemistry (IHC) assesses HER2 protein levels, with a score of 3+ indicating positive overexpression. A score of 2+ is considered equivocal and requires reflex testing by in situ hybridization (ISH) to confirm gene amplification. IHC 0–1+ is negative. Accurate assessment relies on validated testing standards and adequate tumor tissue.

Clinical implications and treatment rely on this biomarker. In early-stage disease, treatment often combines anti-HER2 therapy with chemotherapy, using regimens that may include trastuzumab and pertuzumab in the neoadjuvant or adjuvant setting. For patients with residual disease after neoadjuvant therapy, ado-trastuzumab emtansine (T-DM1) is commonly used. In metastatic disease, options include trastuzumab with chemotherapy, as well as newer agents such as trastuzumab deruxtecan and various tyrosine kinase inhibitors (e.g., lapatinib, neratinib), tailored to prior therapy and tolerability.

Monitoring and safety are important. Cardiotoxicity is a known risk with HER2-targeted therapies, so cardiac function is routinely monitored during treatment. Other adverse effects vary by agent and may include diarrhea, fatigue, rash, or infusion reactions. Overall, the advent of HER2-targeted therapy has significantly improved outcomes for patients with HER2-positive cancers.