A Well-Differentiated Extraskeletal Osteosarcoma: A Case Report

ABSTRACT

A well-differentiated extraskeletal osteosarcoma is very rare, and only seven cases have been reported in the English language clinical literature. We report an additional case of this rare tumor. A 71-year-old man had noticed a mass in the left pubic area for ten years. A CT scan demonstrated the presence of a lobulated calcified mass within the soft tissue. A 5 cm-sized well-circumscribed mass was excised. Histologically the tumor was composed of mature collagenous tissue and bony trabeculae rimmed by osteoblasts. After 43 months, the tumor recurred at the same site and was re-excised. The re-excised tumor contained focal areas of higher cellularity and atypism. We believe that this is the first case of well-differentiated extraskeletal osteosarcoma reported in Korea.