Immunopharmacology and Immunotoxicology, 30:609–621, 2008 Copyright © Informa UK, Ltd. ISSN: 0892-3973 print / 1532-2513 online DOI: 10.1080/08923970801949265 LIPI 0892-3973 1532-2513 Immunopharmacology and Immunotoxicology, Vol. 00, No. 0, April 2008: pp. 1–16 Immunopharmacology and Immunotoxicology Expression of Proto-Oncogene C-Kit and Correlation with Morphological Evaluations in Canine Cutaneous Mast Cell Tumors Expression of Proto-Oncogene C-Kit L. Passantino et al. Letizia Passantino, 1 Giuseppe Passantino, 1 Attilio Cianciotta, 1 Maria Rosaria Ribaud, 1 Giuseppe Lo Presti, 1 Girolamo Ranieri, 2 and Antonella Perillo 1 1 Department of Animal Health and Welfare, Faculty of Veterinary Medicine, University of Bari, Bari, Italy 2 National Cancer Institute, Bari, Italy Canine cutaneous mast cell tumor (MCT) is very common disease in dogs, this is more aggressive than in other species. The biologic behavior of MCT is highly variable and a more accurate prognosis for these tumors needs to performed. The proto-oncogene c-kit is known to play a critical role in development and function of mast cells (MC). The aim of this study was to evaluate the expression of immunohistochemical pat- tern of c-kit in MCTs and to correlate these results with MC density (MCD) and intra- tumoral microvessel density (MVD). Our results confirm that a more aggressive biologic behavior of canine MCT is associated with the increased c-kit expression, fur- ther suggesting a new role for c-kit, as a useful marker, in diagnostic pathology and in tumor progression. Keywords Mastocytomas, Morphometry, Cytochemistry, C-kit, Dog. INTRODUCTION Canine cutaneous mast cell tumors (MCTs) represent very common neoplasms in dogs (7–21% among cutaneous canine tumors), with no sexual background. (1–4) The breeds considered to be most susceptible are Boxer, Boston, Bull terriers, Labrador Retriever, and the mean age of affected dogs is 8.5 years. (5) The Address correspondence to L. Passantino, Dipartimento di Sanità e Benessere Animale, Facoltà di Medicina Veterinaria, Str. Prov.le per Casamassima Km 3, 70010, Valenzano (BA), Italy; E-mail: l.passantino@veterinaria.uniba.it