Cancer is not contagious in the conventional sense. It cannot be transmitted from one person to another by breathing the same air, sharing a toothbrush, touching, kissing, or having sex. With a few rare exceptions (such as organ transplant recipients and mother-to-fetal transmission), the immune system will recognize and destroy any foreign cells (including cancer cells from another person).
Read more here: https://www.verywellhealth.com/is-cancer-contagious-514238
