Microscopically, the results of the immunohistochemical staining revealed that the tumor cells were positive for cyclin-dependent kinase 4 (CDK4) (Fig. 4F), mouse double minute 2 homolog (MDM2) (Fig. 4G) and P16 (Fig. 4H), but negative for cytokeratin (CK) (Fig. 4J), retinoblastoma protein (Rb) (Fig. 4K), and SRY-box transcription factor 10 (SOX-10) (Fig. 4L). Here, CDK4 is linked to neoplasm.