Aggressive chemotherapy and radiotherapy can cure cancer in young female patients, but they can also result in the loss of ovarian function. For these young survivors, both recovery of ovarian function and reproductive potential after treatment have become important quality of life issues. Ovarian tissue cryopreservation (OTC), followed by transplantation after cancer remission is the most commonly applied fertility restoration approach in prepubertal females and women who require immediate cancer therapy. A major concern of frozen-thawed ovarian tissues (FTOT) autotransplantation in cancer survivors is the reintroduction of malignant cells that may have metastasized to the graft. There are several detection methods for minimal residual diseases (MRD) in ovarian cortex tissues. The aim of this paper is to review the available data describing the safety of transplantation of FTOT from cancer patients, focusing on the methods used to detect tumor cells in ovarian tissues and future perspectives in this field.