There are many examples out there of people doing that with cells from tissue, here is one from https://www.wipo.int/wipo_magazine/en/2006/05/article_0008.h...:

"Mr. John Moore suffered from hairy-cell leukemia. In 1976, Dr. David Golde of the University of California Medical Center, recommended that his spleen be removed in order to slow the progress of the disease. Mr. Moore signed a written consent form authorizing a splenectomy, and surgeons removed his spleen. Dr. Golde and his research assistants extracted tissue from the discarded spleen, having recognized its value for research to develop possible ant-cancer treatments. In the next three years they established a cell line from the extracted T-lymphocytes. Mr. Moore was not informed about the research work or the potential of the cell line. In 1984 Dr. Golde was granted US patent 4438032 on the cell line, which generated substantial revenue through commercial arrangements with two biotech firms."