*Purpose: To report 3 cases of donor-derived synovial sarcoma (SS) by a single multiorgan donor in China.

*Methods: SS was diagnosed by the presence of SS18 gene rearrangement. Donor-derived malignancy (DM) was proven by DNA microsatellite.

*Results: The donor was a 14-year-old girl who developed a big intrathoracic tumor. In October 2017, she died of respiratory failure and donated a liver and two kidneys. Pathological result before organ procurement showed solitary fibrous tumor (SFT). All of the three recipients developed SS after organ transplantation. Recipient 1 was a 43-year-old male who received the left kidney. 9 months after transplantation, multiple lesions in the allograft kidney were found and SS was confirmed after allograft nephrectomy. 4 months later, pulmonary metastases were found and he received targeted therapy. After the warning of DM, regular tumor screening was performed for recipient 2 who was a 33-year-old male and received the right kidney. He developed a single lesion in the allograft kidney 13 months after transplantation and biopsy showed the same result with recipient 1. He received radiofrequency ablation. However, tumor recurrence was found 6 months later and allograft nephrectomy was performed. 2 weeks later, pulmonary metastases were found and he received targeted therapy. SS was also found in allograft liver 3 months after transplantation in recipient 3 who was a 26-year-old female with primary liver cancer and partial hepatectomy was performed. Recurrence was found 11 months after partial hepatectomy. 3 months later, systemic metastases were found and she died 2 months later.

*Conclusions: Intrapulmonary SS is sometimes easy to be misdiagnosed as SFT, leading to unexpected DM. The donor diagnosed with benign tumor should also be used cautiously and precise assessment before organ procurement is essential.

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