Veterinary Research Communications, 27 Suppl. 1 (2003) 707–709 © 2003 Kluwer Academic Publishers. Printed in the Netherlands Diagnostic and Prognostic Features of Feline Cutaneous Mast Cell Tumours: A Retrospective Analysis of 40 Cases E. Lepri*, G. Ricci, L. Leonardi, M. Sforna and L. Mechelli Department of Biopathological Sciences, Section of Veterinary Pathology and Hygiene, Faculty of Veterinary Medicine, University of Perugia, Italy * Correspondence: Dipartimento di Scienze Biopatologiche Veterinarie, Sezione di Patologia e Igiene Veterinaria, Facolta ` di Medicina Veterinaria, via S.Costanzo, 4, 06126, Perugia, Italia E-mail: pgpatvet@unipg.it Keywords: cat, cutaneous mast cell tumour, skin, tumour INTRODUCTION The mast cell tumour (MCT ) is a quite frequent neoplasm in cats; the cutaneous form (CMCT) comprises up to 21% of all feline skin tumours and represents the 2nd–4th most frequent neoplasm of this tissue (Miller et al., 1991). Feline CMCTs are usually considered benign, but a recurrence rate of up to 36% has been reported (Buerger et al., 1987). Metastases are infrequent but may occur in 22% of cases (Carpenter et al., 1987). In order to characterize the histological features of prognostic signifi- cance, some authors have focused on the histological type (mastocytic vs histiocytic; Wilcock et al., 1986), pattern of growth (compact vs diffuse; Holzinger et al., 1973), mitotic activity (Yager and Scott, 1993) and lymphocytic infiltrates (Buerger and Scott, 1987). The features considered in each study were different, and no significant results have been obtained. Patnaik’s grading system for canine MCT is not useful in predicting the behaviour of its feline counterpart (Molander-McCrary et al., 1998). A recent report failed to correlate cellular pleomorphism to a worse prognosis ( Johnson et al., 2002). The aim of this study is to perform a retrospective analysis of feline CMCTs in order to characterize histological features of prognostic significance. MATERIALS AND METHODS 42 cases of feline CMCT, observed between 1996 and 2001, were selected from our archives and revaluated. They were collected from 40 cats, two of which presented multiple tumours. Formalin fixed and paraffin embedded tumours were stained with H-E, Gliemsa, toluidine blue and PAS. 707