BMC Cancer Research article A comparative study between mixed-type tumours from human salivary and canine mammary glands Marisa CLS Genelhu1,2,3, Sérgio V Cardoso4, Helenice Gobbi2 and Geovanni D Cassali*1 BioMed Central Open Access Address: 1Laboratory of Comparative Pathology, Biological Sciences Institute, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil, 2Department of Pathology and Forensic Medicine, School of Medicine, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil, 3Immunology Research Laboratory, Vale do Rio Doce University, Governador Valadares, Minas Gerais, Brazil and 4Department of Dentistry, State University of Montes Claros, and Oral Pathology Laboratory, School of Dentistry, Federal University of Uberlândia, Minas Gerais, Brazil Email: Marisa CLS Genelhu - genelhumc@uol.com.br; Sérgio V Cardoso - cardososv@hotmail.com; Helenice Gobbi - hgobbi@medicina.ufmg.br; Geovanni D Cassali* - cassalig@icb.ufmg.br * Corresponding author Published: 28 November 2007 BMC Cancer 2007, 7:218 doi:10.1186/1471-2407-7-218 This article is available from: http://www.biomedcentral.com/1471-2407/7/218 Received: 21 November 2006 Accepted: 28 November 2007 © 2007 Genelhu et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Abstract Background: In comparative pathology, canine mammary tumours have special interest because of their similarities with human breast cancer. Mixed tumours are uncommon lesions in the human breast, but they are found most frequently in the mammary gland of the female dogs and in the human salivary glands. The aim of the study was to compare clinical, morphological and immunohistochemical features of human salivary and canine mammary gland mixed tumours, in order to evaluate the latter as an experimental model for salivary gland tumours. Methods: Ten examples of each mixed tumour type (human pleomorphic adenoma and carcinomas ex-pleomorphic adenomas and canine mixed tumour and metaplastic carcinoma) were evaluated. First, clinical and morphologic aspects of benign and malignant variants were compared between the species. Then, streptavidin-biotin-peroxidase immunohistochemistry was performed to detect the expression of cytokeratins, vimentin, p63 protein, estrogen receptor, β-catenin, and E-cadherin. Results: After standardization, similar age and site distributions were observed in human and canine tumours. Histological similarities were identified in the comparison of the benign lesions as well. Metaplastic carcinomas also resembled general aspects of carcinomas ex-pleomorphic adenomas in morphological evaluation. Additionally, immunohistochemical staining further presented similar antigenic expression between lesions. Conclusion: There are many similar features between human salivary and canine mammary gland mixed tumours. This observation is of great relevance for those interested in the study and management of salivary gland tumours, since canine lesions may constitute useful comparative models for their investigations. Page 1 of 9 (page number not for citation purposes)