PCNA and osteosarcoma: Among the chondroblastic osteosarcoma cells, the proliferating malignant chondroblastic osteosarcoma was identified by the expression of the gene-regulating tumor cell cycle, including TOP2A, PCNA, TYMS, and MKI67. On the other hand, two subclusters were hypertrophic chondroblastic cells that elevated the expression of the MEF2C, PTH1R, and IHH genes.