Figure 3 Immunohistochemical panel of the tumor (all with magnification ×100)(A) B-cell lymphoma 2 (BCL-2): focal positivity. (B) Low-molecular-weight cytokeratin antibody CK8/18 (CAM5.2): negative (rare weak-positive cells). (C) CD34: restricted to vascular endothelium (internal control). (D) Cytokeratin: negative (rare weak-positive cells). (E) Desmin: negative. (F) Ki-67 proliferation: approximately 30% labeling index. (G) Tumor suppressor protein (p53): diffuse strong nuclear staining (mutant-type pattern). (H) S100 protein family: focal positivity. (I) Special AT-rich sequence-binding protein 2 (SATB2): diffuse nuclear positivity. (J) Smooth muscle actin (SMA): focal positivity. (K) Signal transducer and activator of transcription 6 (STAT6): negative. Epithelial membrane antigen (not shown) was also negative. The overall IHC profile supports osteoblastic differentiation and argues against epithelial, vascular, and solitary fibrous tumor lineages.