Stem cells isolated from adult tissue samples or extraembryonic tissues are not tumorigenic. Hundreds of preclinical and clinical studies have confirmed this fact. However, the patient's existing oncology is a contraindication to stem cell therapy.
Please take a look more information here:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6566307/
https://www.ema.europa.eu/en/documents/scientific-guideline/questions-answers-allogenic-mesenchymal-stem-cell-based-products-veterinary-use-specific-questions_en.pdf
https://www.researchgate.net/publication/236251279_Risk_of_tumorigenicity_in_mesenchymal_stromal_cell-based_therapies-Bridging_scientific_observations_and_regulatory_viewpoints