Comparison of p63 and p73 expression in benign and malignant salivary gland lesions

BACKGROUND: The p63 and p73 genes are members of the p53 family and play an important role in stem cell identity and cellular differentiation and are expressed in basal and myoepithelial cells. In this study, we examined the expression of p63 and p73 in 50 various benign salivary gland lesions and 45 malignant salivary gland tumors. METHODS: The 95 salivary gland tumors were selected from the archives of the Department of Pathology and Laboratory Medicine at the Hospital of the University of Pennsylvania. Sectioned formalin-fixed paraffin-embedded tissue cut at 3 mum was immunostained with antibodies that recognize all isozymes of p63 and p73 and evaluated with respect to percentage of positive cells and localization. RESULTS: In benign lesions, p63 and p73 nuclear reactivity was seen in 46 (92%) of 50 and 47 (94%) of 50 cases, respectively. In malignant tumors, p63 and p73 were seen in 34 (76%) of 45 and 40 (89%) of 45 cases, respectively. A significant difference between p63 and p73 positivity was only seen in adenoid cystic carcinomas (p = .006). Also, p73 was found in tumors with minimal basal/myoepithelial differentiation. CONCLUSIONS: Hence, p63 and p73 expression is retained in both benign and malignant salivary gland tumors with basaloid or myoepithelial differentiation. Hence, p63 seems to be a more specific marker of myoepithelial differentiation than p73.