A drug used to treat melanoma that has recurred (come back) after surgery. It is used in patients whose cancer is in the skin and lymph nodes and cannot be removed by surgery. It is also being studied in the treatment of other types of cancer. T-VEC is made with a form of the herpesvirus that has been changed in the laboratory to infect and break down cancer cells without harming normal cells. It may also help the immune system kill cancer cells. T-VEC is injected directly into tumors in the skin and lymph nodes. It is a type of oncolytic virus therapy. Also called Imlygic and talimogene laherparepvec.