RB1 and pleomorphic liposarcoma: Along with the histologic appearance of the mass, this evaluation should include testing for expression of CD34, CDK4, MDM2, STAT6, and RB to distinguish well-differentiated liposarcomas from other conditions, such as laryngeal lipomas, solitary fibrous tumors, dedifferentiated liposarcomas, and pleomorphic liposarcomas [4,6-8].