Since heterozygous H3F3A c. 103G>T (p. Gly34Trp) mutation was detected not only in the biopsy sample from the primary site with typical GCTB and high-grade sarcoma components but also in the resected material from the metastatic site with only pure high-grade sarcoma component, the tumor was considered originally derived from conventional GCTB and acquire malignant transformation to high-grade sarcoma.