In conclusion, the novel combination of T-VEC with nivolumab and ipilimumab as a neoadjuvant treatment for HER2-negative early-stage breast cancer showed antitumor activity at the cost of irreversible long-term toxicities, with type 1 diabetes mellitus in 1 patient and hypothyroidism in 3 patients. The gene discussed is ERBB2; the disease is hypothyroidism.