Immunohistochemical expression of ΔNp63 versus pan-p63 in normal and neoplastic feline tissues

ΔNp63 is an isoform of p63 that plays an essential role in the development and growth of some epithelial tissues. In this study, we investigated the expression of ΔNp63 in normal and neoplastic tissues of cats and compared the results with the expression of pan-p63. Immunohistochemistry for ΔNp63 and pan-p63 was performed in normal tissues from 2 adult cats and in 10 cases each of 22 different types of feline neoplasms. In normal tissues, there was nuclear ΔNp63 immunolabeling in basal cells of stratified squamous, transitional, and pseudostratified columnar epithelia; basal cells of sebaceous glands; trophoblasts; and myoepithelial cells. Of the neoplasms, 10/10 apocrine ductal adenomas, 10/10 mammary ductal carcinomas, 10/10 pulmonary adenosquamous carcinomas, 10/10 squamous cell carcinomas, 10/10 trichoblastomas, and 10/10 urothelial carcinomas immunolabeled for ΔNp63. The ΔNp63 immunolabeling was diffuse in almost all neoplastic cells with squamous, basal, and urothelial origins. In the neoplasms with ductal differentiation, only the neoplastic suprabasal myoepithelial cells immunolabeled. Application of pan-p63 to the same set of neoplasms revealed positivity not only in the same neoplasms, but also in several unexpected tumor types (3/10 exocrine pancreatic carcinomas, 3/10 fibrosarcomas, 3/10 pulmonary adenocarcinomas, 2/10 lymphomas, 1/10 cholangiocarcinomas, 1/10 hemangiosarcomas, 1/10 mast cell tumors, and 1/10 meningiomas). Both ΔNp63 and pan-p63 antibodies demonstrated 100% diagnostic sensitivity and negative predictive value for diagnosing feline neoplasms with squamous, basal, and urothelial epithelia or myoepithelial cells. However, ΔNp63 showed higher diagnostic specificity (100% vs. 90.6%), positive predictive value (100% vs. 80%), and overall accuracy (100% vs. 93.1%) compared with pan-p63.