We report this rare case to raise clinical awareness, accumulate diagnostic and treatment experience, and offer guidance for managing similar cases in the future.<h4>Methods</h4>We present a 79-year-old woman with large invasive vulvar Paget's disease (HER2 3+).<h4>Results</h4>As surgery was not feasible, she received trastuzumab plus capecitabine, achieving marked tumor shrinkage. Here, ERBB2 is linked to neoplasm.