Parathyroid Carcinoma Disseminated Following Endoscopically-Assisted Surgery: A Case Report

Endoscopically assisted surgery for parathyroid tumors has provided excellent cosmetic results and has been covered by Japan's national insurance system since 2016. However, careful handling is essential because parathyroid tumor cells can easily disseminate.

We herein report the case of a 34-year-old woman who developed widespread dissemination of parathyroid carcinoma after endoscopic resection. She initially underwent endoscopically assisted left thyroid lobectomy for an intrathyroidal parathyroid tumor, which was later diagnosed as a carcinoma. Four years later, multiple cervical recurrences and pulmonary metastases were observed. Extensive cervical tumor resection was performed, including en bloc removal of the invaded structures, followed by resection of lung metastases. Despite temporary improvement, the disease progressed. Genomic profiling revealed a CDC73 mutation and high tumor mutation burden. Pembrolizumab therapy achieved temporary stabilization but was eventually ineffective. The patient died during palliative care.

This case highlights the risk of tumor cell dissemination in parathyroid surgery when capsular integrity is compromised. While this risk exists regardless of the surgical approach, certain technical factors associated with endoscopically assisted procedures may increase the likelihood of inadvertent capsular injury. Complete en bloc resection during the initial operation is essential for parathyroid carcinoma, because incomplete resection leads to poor prognosis. When carcinoma is suspected intraoperatively, surgeons should consider open surgery. Comprehensive genomic profiling may provide therapeutic options such as immune checkpoint inhibitors for recurrent or metastatic cases.