Here, we describe an exceptional response to trastuzumab deruxtecan in a HER2-expressing, advanced, recurrent OCCC that was treated in the Molecular Mechanisms of Tumor Evolution and Resistance to Therapy (MMTERT) observational study, which aims to identify actionable alterations in serial tumor samples using multiomic analytics.8 Written informed consent was obtained from the patient for the publication of this article. The gene discussed is ERBB2; the disease is neoplasm.