MUC4 and carcinoma: This locus encodes the highmolecular weight transmembrane mucin MUC4, which shows aberrant expressionin a variety of carcinomas.23 MUC4 is mainlyexpressed in airway epithelial cells for protection and lubrication,and plays important roles in cell signaling, proliferation and differentiation.24 Mucins contain heavily glycosylated centraldomains, composed of a variable number of tandem repeats.