Primary synovial sarcoma is a soft tissue tumor which originates from synoviallike undeveloped mesenchymal structures. Here, we report the case of a giant mediastinal sarcoma in a 41-year-old female patient. After diagnosis, she underwent neoadjuvant chemotherapy. Due to its low efficacy, we collegially decided to undergo cytoreductive debulking surgery. The mass invaded the phrenic nerve bilaterally and its excision caused a severe lesion of the left nerve and a partial impairment of the right one. Thus, plastic surgeons decided to reconstruct the right phrenic nerve employing the contralateral remaining fibers. The invasiveness of this tumor, its difficult removal, histological profile and the peculiar technique to preserve diaphragmatic function classify this case as very rare. The therapeutic strategy was based on interdisciplinary teamwork which comprised several specialists' opinions. Our strategy allowed us to pursue the challenging objective to give a young woman with a severe diagnosis the best possible chance of achieving a good quality of life. To the best of our knowledge, this phrenic nerve reconstructive technique is very rare and has not previously been reported in the literature. The report emphasizes that it is possible to deal with an apparently impossible case through a collaborative approach involving several different medical specialist professionals.