Histopathological evaluation of canine mammary gland tumours: a study of 92 cases

Abstract

Neoplasms of the mammary glands are the most common tumours in female dogs, albeit rare cases in male dogs are reported as well. Canine mammary tumours (CMT) are a naturally occurring heterogeneous group of cancers with a high incidence rate of up to 25-50% among females. Despite many years of research, the aetiology and high incidence of these tumours are still poorly understood. There is a need to present epidemiological data on mammary tumour occurrence in different breeds of dogs in different countries to select prognostic risk factors and identify breeds with higher susceptibility to tumour development. The aim of this study was to describe histopathological findings for 92 animals, including 87 female and five male dogs, diagnosed with mammary gland tumours (MGTs) in Poland and to determine such epidemiological characteristics as age, breed and size as well as their relationship with tumour incidence and malignancy. Histopathological analyses showed that 82 (89.1%) of the 92 dogs had malignant tumours, seven dogs (7.6%) had benign tumours, and three dogs (3.3%) had non-neoplastic changes in the form of dysplasias. Thirty (33.7%) of the 89 dogs with mammary gland tumours had more than one neoplasia. The highest number of cases were epithelial tumours (79.8%), followed by mesenchymal (14.6%) and mixed (5.6%) tumours. The vast majority of malignant tumours were tubulopapillary carcinomas (33.7%), complex carcinomas (24.7%) and solid carcinomas (11.2%). It is worth noting a large variation in the degree of tumour malignancy among the tubulopapillary carcinoma cases. The present study showed a higher incidence of mammary gland tumours in female dogs aged 8-13 years. The vast majority of female cases were diagnosed at the age of 12 years. The average year of surgical intervention in the male dogs was 9 years. Among 25 breeds of dogs in which MGTs were noted, the highest number of affected animals were crossbreeds (30.3%), German Shepherds (23.6%) and English Cocker Spaniels (9.0%). The large size of the tumour (≥ 5 cm) was strongly associated with its malignancy.

Occurrence of mammary gland tumours in male dogs and its weak association with development of testicular tumours: a review

“…0.5–2.7%, usually < 1% (Bearss et al 2012 ; Lather et al 2017 ). However, the available data indicate that, depending on the country and the size of the tested group, the incidence of male MGTs varies from 0.5% (4/341) in Croatia (Šoštarić-Zuckermann et al 2013 ), 1.7% (6/357) in Canada (Mitchell et al 1974 ), 2.2% (25/1142) in Italy (Merlo et al 2008 ), 2.5% (2/79) in South Korea (Chae et al 2007 ), and 2.6% in China (13/504)(Zheng et al 2022 ) to 5% (3/63) in India (Dhami et al 2010 ; Lather et al 2017 ) and Poland (5/92) (Tkaczyk-Wlizło et al 2023 ).…”

“…The occurrence of MGTs in male dogs is definitely not as common as in bitches, but many cases of this disease have been reported over the years (Bearss et al 2012 ; Han et al 2016 ; Jabara 1969 ; Lather et al 2017 ; Tkaczyk-Wlizło et al 2023 ). Interestingly, in some cases of MGTs, also testicular tumours (TTs) and/or testicular abnormalities were observed (Kwon et al 2017 ; Muscatello et al 2021 ; Walker 1968 ; Warland et al 2011 ; Zuchi et al 2018 ).…”

Mutations and polymorphisms in mitochondrial genome of dogs with solid mammary carcinoma – a preliminary study

“…One example is solid mammary carcinoma, which is among the most common (11% of all diagnosed) and most difficult to treat, especially because it is not clearly separated from healthy tissue (4,32). In order to predict the progression of the disease, mammary tumors have been characterized on the basis of, among others, the level of tubule formation, the number of tissue cells in mitosis, and differences in the structure of the nucleus.…”