CDK4 and neoplasm: On immunohistochemical staining, the tumor cells were found to be diffusely positive for α-smooth muscle actin (α-SMA) (Fig. 5d), desmin (Fig. 5e), and caldesmon (Fig. 5f) and negative for CD34, S100, c-kit, MDM2, and cyclin-dependent kinase 4 (CDK4).