CDK4 and neoplasm: Pathologically, the chest wall tumor showed necrotic foci and almost no viable cells (Fig. 3a); however, immunohistochemical staining revealed murine double minute 2 (MDM2) and cyclin-dependent kinase 4 (CDK4)-positive nuclear cells with irregularities in nuclear size and bizarre nuclear morphology, as shown in Figs. 3b and c.