Mutation distribution and subtype frequencies were compared with global and regional datasets.<h4>Results</h4>Baseline cfDNA levels were significantly elevated in breast cancer patients compared to controls (p < 0.001), with highest levels in TNBC (Triple-negative breast cancer) and HER2-enriched subtypes and lowest in Luminal A. Follow-up cfDNA remained persistently elevated in aggressive subtypes and TP53-mutated cases, suggesting molecular residual disease. The gene discussed is ERBB2; the disease is breast cancer.