Aside GSDMs, there are other frequently amplified genes near the HER2 amplicon that could affect HER2 BC clinical behavior, such as TOP2A (in 17q21.2 [192]) or genes within the 17q23 amplicon such as RPS6KB1, PPM1D, or MIR21 [193,194]. The gene discussed is PPM1D; the disease is breast cancer.