Purpose: To highlight the imperative of informed consent in the fertility preservation of cancer patients before ovarian tissue autotransplantation. Methods: Three papers of tumor recurrence after autotransplantation of frozen-thawed ovarian tissue were compared with the main papers before tumor recurrence was reported in the cancer patients. Results: Histology was performed before autotransplantation in cases 1 and 3, but not in case 2. Histology alone is insufficient for the detection of minimal residual disease (MRD). Furthermore, transplanted ovarian tissue is different from that examined for MRD detection, and how much of the resected ovarian tissue was examined for MRD detection is unclear. The possibility that grafted tissue caused tumor recurrence cannot be ruled out in any of the three cases, because autotransplantation in cancer patients, at present, uses ovarian tissue different from that examined for MRD. Conclusions: We recommend informed consent for cancer patients, because: 1) the transplanted ovarian tissue is different from the ovarian tissue examined for MRD detection; 2) the amount of resected ovarian tissue analyzed for MRD is very small; and 3) MRD detection methods vary. In conclusion, freezing and storage of ovaries should be encouraged, transplantation must be performed carefully, and informed consent is essential.