In immunohistochemistry for neuron-specific enolase (NSE), the patient's primary tumor (E) showed a strong positive expression, but staining in frozen-thawed ovarian tissue (F) and ovarian tissue after long-term grafting (G, H) were negative. Sir, Safety issues surrounding reimplantation of ovarian tissue retrieved at the time of a cancer diagnosis have been a cause of concern for many years.1-3 Here, we report a case of a central nervous system (CNS) primitive neuroectodermal tumor (PNET) relapse 6 years after ovarian tissue transplantation. [Extracted from the article]