BMC Cancer 2007, 7:218 http://www.biomedcentral.com/1471-2407/7/218 yFHliignstuaornpedat1ehoosloingi(cHalEa)sspteaicnt;soorfigbinenaligmnaagnndifimcaatliiogna,n1t0×mixed tumours of human salivary and canine mammary glands by haematox- Histopathological aspects of benign and malignant mixed tumours of human salivary and canine mammary glands by haematox- ylin and eosin (HE) stain; original magnification, 10×. (A) Pleomorphic adenoma in human salivary gland; (B) Mixed tumour in canine mammary gland; (C) Carcinoma ex-pleomorphic adenoma in human salivary gland; (D) Metaplastic carcinoma in canine mammary gland. cords, nests, or even isolated, but irregularly dispersed in a predominantly myxoid or myxo-chondroid matrix. MC were observed to be histomorphologically similar to the adenocarcinoma NOS (not-otherwise specified) or to undifferentiated carcinoma-type Ca ex-PA, since both were infiltrative lesions with malignant degeneration areas, characterized by cell pleomorphism (ovoid to poly- hedral cells with clear to hyaline cytoplasm), and hyper- chromatic or vesiculated nuclei with conspicuous nucleoli. Immunohistochemical assays displayed positive cytoplas- mic localization of cytokeratins in all neoplastic cells from all lesions. Vimentin was identified in the cytoplasm of non-luminal cells of ductal formations, in plasmacytoid and spindle cells of PA and canine MT, in all MC cells, and was identified diffusely in Ca ex-PA with myoepithelial differentiation (those which the malignant component was described as myoepithelial, adenoid cystic, and poly- morphous low-grade adenocarcinomas). All PA presented positive p63 nuclear immunolocaliza- tion in neoplastic luminal, plasmacytoid and spindle cells, while p63 was found in only five samples of Ca ex- PA (two samples with diagnosis of myoepithelial carci- noma, two with adenoid cystic carcinomas, and one with undifferentiated carcinoma). All canine MT and MC depicted positive p63 expression, in a similar fashion to that seen in PA, while the malignant lesion had less posi- tive cells and these presented less intense reaction (Figure 2). The decrease in immunopositivity frequency in Ca ex- PA was significantly different regarding all the other groups (p < 0.05). β-catenin expressions in neoplastic epithelial cells of both PA of human salivary gland and MT of canine mammary glands have shown to be similar in location, to the expres- sion in normal glandular parenchyma (membrane and/or cytoplasmic). Membrane and cytoplasmic β-catenin immunolocalization was especially frequent in cells of ductal formations in these benign tumours. In malignant lesions, nuclear expression of this protein was also identi- fied (Figure 3). No β-catenin expression was observed in highly atypical areas of malignant tumours of both species or in those with rich myxo-chondroid stroma. Page 4 of 9 (page number not for citation purposes)