J. Comp. Path. 2002, Vol. 127, 114±117 doi:10.1053/jcpa.2002.0568, available online at http://www.idealibrary.com on Nuclear Morphometry in Squamous Cell Carcinomas of Canine Skin P. Maiolino, B. Restucci, S. Papparella and G. De Vico  Dipartimento di Patologia e Sanita Á Animale, Settore di Anatomia Patologica, Facolta Á di Medicina Veterinaria, Universita Á degli Studi di Napoli Federico II, Via Delpino 1, 80137 Napoli and *Istituto di Patologia Generale e Anatomia Patologica Veterinaria, Facolta Á di Medicina Veterinaria, Universita Á di Messina, Italy Summary To investigate the diagnostic and prognostic value of nuclear morphometry in squamous cell carcinomas (SCCs) of canine skin, histological samples from 15 dogs were retrospectively analysed by computerized nuclear morphometry. In each case, the nuclei of at least 100 neoplastic cells were measured, and the mean nuclear area (MNA), standard deviation of MNA (SDa), mean nuclear perimeter (MNP), standard deviation of MNP (SDp), nuclear form factor (FF), and standard deviation of FF (SDf ) were calculated. The morphometric data were examined in relation to tumour histological grade. No statistical differences were found between the different grades of SCC in terms of the mean values of SDa, SDp, FF or SDf. The MNA values, however, differed significantly between grades: I and III; I and IV; II and III; II and IV. The MNP values differed significantly between grades: I and III; I and IV; II and IV. The results indicate that nuclear morphometry analysis is a simple and reproducible method that could be used to provide objective diagnostic criteria for cutaneous SCCs in the dog. # 2002 Elsevier Science Ltd. All rights reserved. Introduction Cutaneous squamous cell carcinoma (SCC) is a common tumour which accounts for 54% of all cutaneous neoplasms in dogs (Bostock, 1986). Canine SCCs differ strikingly in behaviour, depending on their location. SCCs of the skin are locally invasive but have a low metastatic potential. In contrast, SCCs of the toe have a greater tendency to recur and metasta- size (Weiss and Frese, 1974). In this regard, recurrence and metastasis seem to be related to the degree of differentiation of the neoplastic cells, being more likely to occur with poorly differentiated tumours (Goldschmidt and Shofer, 1992). However, nuclear grading, which expresses the degree of nuclear differ- entiation of neoplastic cells (Black and Speer, 1957), has been put forward as an important diagnostic and prognostic factor in tumours but often lacks objectivity and, in the hands of different pathologists, reproducibility (Baak et al., 1982). Therefore, the current trend is to quantify nuclear features by morphometric and other methods that are objective and reproducible (Sorensen, 1992) and can detect changes not immediately apparent to the naked eye (Hamilton and Allen, 1995). Recent studies of human tumours (breast carcinoma, colorectal carcinoma, renal cell carcinoma, intra-oral squamous cell carcin- oma, and basal cell carcinoma [Tosi et al., 1986; De Rosa et al., 1990; Mitmaker et al., 1991; Pienta and Coffey, 1991; Bundgaard et al., 1992]) have demon- strated the value of the morphometric method in prognosis and as an indicator of malignant potential. Little is known about this field of investigation in veterinary medicine (Destexhe et al., 1995; De Vico and Maiolino, 1997; Roels et al., 2000). The aim of the present study was to investigate whether quantitative measurements of nuclear variables, including area, perimeter and form factor, could be used as objective diagnostic criteria for cutaneous SCCs in the dog. Materials and Methods Animals and Tumour Samples SCC tissue samples from 15 dogs (11 male and four female) of different breeds and age were examined. One digital tumour had given rise to metastasis in the inguinal lymph nodes at the time of diagnosis. The 0021±9975/02/$ ± see front matter # 2002 Elsevier Science Ltd. All rights reserved.