CD44 expression in intraoral salivary ductal papillomas and oral papillary squamous cell carcinoma.

CD44 is a transmembrane adhesion molecule which has been previously shown to be useful in the differentiation of benign papillary lesions from invasive carcinoma in several different areas including sinonasal mucosa and breast tissue. CD44 expression has previously been shown to be lost in invasive carcinoma and retained in benign papillary lesions in both of the above locations. In addition, studies have evaluated oral mucosal lesions for CD44 expression and found a loss with invasive squamous cell carcinoma when compared to normal epithelium, hyperplasia, and squamous papillomas, which stained particularly strongly. To the best of our knowledge, no study has evaluated CD44 expression when comparing salivary ductal papillomas in comparison to oral papillary SCCA. In this study 18 cases of intraductal papilloma were compared to 19 cases of oral papillary SCCA. Within the ductal papilloma group, all cases stained either absent (6%), weakly (33%), or moderately (61%) with 76% expressing the stain diffusely and 24% focally. In comparison, the papillary squamous cell carcinoma cases expressed the CD44 moderately (26%) or strongly (74%) with 100 % showing diffuse staining. Thus, the CD44 expression was contrary to expectation based on previous studies, which we hypothesize is due to the extremely well differentiated nature of papillary SCCA which expressed CD44 staining compatible with levels previously reported with oral squamous papillomas than invasive carcinoma.