Abstract
Mesenchymal chondrosarcoma is a rare tumor that is distinctly different from classic chondrosarcoma. The prognosis of this tumor is poor, with a high incidence of locoregional and distant metastases. It shows a predilection for the head and neck, however mesenchymal chondrosarcoma of hyoid bone has rarely been reported. We experienced a case of mesenchymal chondrosarcoma of the hyoid bone in a 39-year-old woman. She underwent excision of the tumor by right hemihyoidectomy. Histologically, a combination of cellular zones composed of undifferentiated small cells and chondroid zones typically presented a bimorphic appearance. CD99 (DN16) immunohistochemical stain demonstrated that all undifferentiated small cells had strong reactivity with a distinct membranous pattern. There was microscopic tumor extension to the resection margin of the hyoid bone, however, no evidence of reccurence is noted at follow-up of 4 months with neck CT.