[1258] Comparison of p63 and p40 (ΔNp63 Isoform) as Basal and Myoepithelial Markers in Salivary Gland Tumors

Cristina E Aguilar, Raja R Seethala. University of Pittsburgh Medical Center, Pittsburgh, PA

Background: Immunohistochemical staining for p63, a p53 homologue, is frequently used in the clinical setting to confirm squamous, basal or myoepithelial differentiation in a variety of organ sites. There are two main isoforms of p63: TAp63 and ΔNp63, both of which are recognized by the most commonly used antibody to p63, clone 4A4. Recent studies in lung tumors have called into question the specificity of this p63 antibody for squamous differentiation and have demonstrated that an antibody directed towards only ΔNp63 isoforms (p40) has better performance in this respect. We herein performed a similar survey in salivary gland tumors to compare the performance of both p63 and p40 antibodies as markers of basal and myoepithelial differentiation.
Design: Nineteen salivary gland tumors, 15 with adjacent normal salivary tissue, were stained with p63 (BC4A4, prediluted, Biocare) and p40 (5-17, 1:1000, Calbiochem). Tumors were broadly categorized as ductal (n=7; 1 canalicular adenoma, 1 salivary duct carcinoma ex pleomorphic adenoma, 1 mammary analogue secretory carcinoma, and 4 adenocarcinomas NOS), biphasic (n=7; 1 adenoid cystic carcinoma, 2 myoepithelial carcinomas ex pleomorphic adenoma, 1 epithelial-myoepithelial carcinoma, 1 pleomorphic adenoma; 1 basal cell adenoma, and 1 basal cell adenocarcinoma), composed of ductal and myoepithelial/basal elements, purely myoepithelial (n=4; 1 myoepithelioma and 3 myoepithelial carcinomas) and one mucoepidermoid carcinoma (presumed excretory duct phenotype). Nuclear staining was considered positive.
Results: Both p63 and p40 stained the myoepithelial cells surrounding acini and intercalated ducts as well as the basal cells of the striated and larger excretory ducts. All biphasic and myoepithelial tumors showed a similar distribution of reactivity and intensity in the basal and myoepithelial cells for both p63 and p40. In the mucoepidermoid carcinoma, p63 and p40 highlighted epidermoid and intermediate cells in a similar distribution and intensity. However, 3/7 tumors regarded as ductal tumors showed focal p63 positivity, but no p40 expression. These consisted of a minimally invasive adenocarcinoma ex pleomorphic adenoma, one adenocarcinoma NOS, and one canalicular adenoma.
Conclusions: Overall, p40 has a similar distribution to p63 in both normal salivary gland and salivary gland neoplasms. However, p40 does appear to be more specific with respect to a subset of ductal tumors of the salivary gland.
Category: Head & Neck

Tuesday, March 5, 2013 9:30 AM

Poster Session III # 152, Tuesday Morning


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