However, osteocalcin, a marker of advanced osteoblastic differentiation, is notably absent in highly purified GCTB stromal cell populations, suggesting the presence of an intrinsic or extrinsic block to osteoblastic differentiation within the tumor in vivo, potentially related to factors produced by the stromal cell population and/or the osteoclast-like giant cells [20,26]. This evidence concerns the gene BGLAP and neoplasm.