Canine cutaneous tumours from three southwestern states of Nigeria: a retrospective study.

Over the years, studies have shown that the skin is the most commonly affected organ for both neoplastic and non-neoplastic conditions (Broden et al., 2010). This occurrence has been attributed to continuous exposure of the skin to physical, chemical, and environmental factors (Guzman et al., 2003; Pakhrin et al., 2007). Cutaneous tumours are the second most frequently diagnosed cancer in dogs resulting in approximately 30% of all tumours reported and are usually excised due to easy surgical access than tumours in other organs (Moraes et al., 2009). Several authors have reported the occurrence of tumours by utilizing data obtained from registries, animal hospital reports, and diagnostic laboratory reports. Most of these reports vary greatly in terms of data sources, sample numbers, the size of geographical regions assessed (Graf et al., 2018; Kok et al., 2019), prevalent environmental influences, and breed populations (Kaldrymidou et al., 2002; Sanja et al., 2005; Pakhrin et al., 2007). Previous studies have shown that dogs are susceptible to tumours at any age and there is a marked predisposition in aged dogs than young dogs because of a progressive accumulation of genetic mutations (Reif, 2007). Environmental chemical contaminants (especially pyrethroids) also have been implicated in the occurrence of mammary adenocarcinomas (Reif, 2007). Ultraviolet light rays have also been studied as a possible aetiology of squamous cell carcinoma (SCC) in animals with poor skin pigmentation (Reif, 2007). In Nigeria, different case reports on canine tumours have been documented (Amber and Ralph, 1982; Faramade et al., 2017), but the risk factors and distribution of the disease in these species are very limited and restricted to the databases of Veterinary Teaching Hospitals of universities and private veterinary clinics in the major cities. The documentation of occurrences of different tumour types in a particular geographical region is necessary because it provides easy access to data for further investigation and helps in prompt diagnosis and management by clinicians (Moraes et al., 2009).