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Mammary gland tumours (MGTs) are commonly occurring neoplasms in female dogs. However, rare cases of MGTs in male dogs have been reported for years. Due to the low incidence of MGTs in male dogs in comparison to female dogs, veterinary oncology is mainly focused on mammary neoplasms diagnosed in female dogs and extensive research is conducted in this scientific area. Therefore, there are no sufficient epidemiological data on male dogs and the aetiology of their tumour development is still poorly understood. The aim of this literature review was to present cases of MGTs in male dogs for better understanding the scale of the problem over the years. The analyses of 74 affected male dogs with 92 tumours showed that the majority of MGTs in male dogs were benign tumours (54.3%), especially in form of adenomas, often developed in posterior canine mammary glands (58.1%). The increased number of canine MGTs in male dogs aged 7 -13 years with an age peak at 11 years was noted. The age of affected animals was not related to breed. Mammary gland neoplasms were diagnosed predominately in Crossbreeds (20.2%) followed by Cocker Spaniels (18.9%) and German Shepherds (10.8%). The association between MGT development in male dogs and co-occurrence of testicular tumours (TTs) has been discussed for years. Thus, cases of development of both tumours were included in this study. As a result, only in 12.7% cases of MGTs also history of TTs was described. Therefore, no general association between these tumours should be assumed. [ABSTRACT FROM AUTHOR]

Dogs spontaneously develop mammary gland tumors (MGT) and exhibit striking similarities in clinical and epidemiological characteristics to human breast cancer (HBC). Descriptive and comparative analysis of HBC and canine MGT with a focus on evaluating similarities and geographical distribution were the aims of this study. HBC cases were obtained from North Regional Oncological Registry (RORENO) (2010-2015) and canine MGT cases from Vet-OncoNet (2019-2022). Analyses were performed based on published and well accepted classification systems (ICD-O-3.2 for humans and Vet-ICD-O-canine-1). Age-standardized incidence risks (ASIR) of Porto district municipalities were calculated using 2021 Portuguese census (INE) and data from the Portuguese animal registration system (SIAC). Among 7,674 HBC cases and 1,140 MGT cases, a similar age and sex distribution pattern was observed. Approximately 69.2% of HBC cases were between 40 and 69 years old, while 66.9% of MGT cases were diagnosed between 7 and 12 years old (mean age of 9.6 years, SD = 2.6). In women, Invasive breast carcinoma (8500/3) was the most common histological type (n = 5,679, 74%) while in dogs it was the Complex Carcinoma (8983.1/3) (n = 205, 39%). Cocker and Yorkshire Terriers exhibited the highest relative risks (3.2 and 1.6, p < 0.05, respectively) when compared to cross breed dogs. The municipalities' ASIR of the two species exhibited a high correlation (R = 0.85, p < 0.01) and the spatial cluster analysis revealed similar geographic hotspots. Also, higher ASIR values both in women and dogs weremore frequently found in urbanized areas compared to rural areas. This research sheds light on the shared features and geographical correlation between HBC and canine MGT, highlighting the potential of cross-species environmental oncology studies. [ABSTRACT FROM AUTHOR]

Simple Summary: Mammary tumors are the most frequent neoplasia in female dogs. They develop spontaneous cancer and share several biological, clinical, pathological and molecular characteristics with cancer diagnosed in humans. Mammary cancer is also one of the leading causes of death in both species. This review provides a detailed description of the histological, molecular and clinical aspects of mammary cancer in canines; it discusses risk factors and currently available diagnostic and treatment options, as well as remaining challenges and unanswered questions. Mammary cancer is the most frequently diagnosed neoplasia in women and non-spayed female dogs and is one of the leading causes of death in both species. Canines develop spontaneous mammary tumors that share a significant number of biological, clinical, pathological and molecular characteristics with human breast cancers. This review provides a detailed description of the histological, molecular and clinical aspects of mammary cancer in canines; it discusses risk factors and currently available diagnostic and treatment options, as well as remaining challenges and unanswered questions. The incidence of mammary tumors is highly variable and is impacted by biological, pathological, cultural and socioeconomic factors, including hormonal status, breed, advanced age, obesity and diet. Diagnosis is mainly based on histopathology, although several efforts have been made to establish a molecular classification of canine mammary tumors to widen the spectrum of treatment options, which today rely heavily on surgical removal of tumors. Lastly, standardization of clinical study protocols, development of canine-specific biological tools, establishment of adequate dog-specific disease biomarkers and identification of targets for the development of new therapies that could improve survival and have less adverse effects than chemotherapy are among the remaining challenges. [ABSTRACT FROM AUTHOR]

Simple Summary: Lymphoma is a common cancer in dogs, with large variation between breeds in both the incidence and frequency of immunophenotypes (B-cell or T-cell lymphoma). Very few studies have explored the genetic underpinnings of lymphoma in dogs, and it is not known whether various breeds share common risk genes considering the disparities in disease occurrence and immunophenotype distribution. In this study, our aim was to investigate lymphoma in a population of Border Collies, a breed at increased risk of lymphoma (often B-cell type). To our knowledge, this is the first genetic investigation of lymphoma risk in Border Collies. We examined pedigree data for possible inheritance patterns, and conducted a genetic investigation that incorporated the pedigree information to uncover possible genetic predispositions for lymphoma. We identified regions on chromosomes 18 and 27 that harbour cancer-related genes as prime candidates for lymphoma susceptibility, warranting further investigation. There has been considerable interest in studying cancer in dogs and its potential as a model system for humans. One area of research has been the search for genetic risk variants in canine lymphoma, which is amongst the most common canine cancers. Previous studies have focused on a limited number of breeds, but none have included Border Collies. The aims of this study were to identify relationships between Border Collie lymphoma cases through an extensive pedigree investigation and to utilise relationship information to conduct genome-wide association study (GWAS) analyses to identify risk regions associated with lymphoma. The expanded pedigree analysis included 83,000 Border Collies, with 71 identified lymphoma cases. The analysis identified affected close relatives, and a common ancestor was identified for 54 cases. For the genomic study, a GWAS was designed to incorporate lymphoma cases, putative "carriers", and controls. A case-control GWAS was also conducted as a comparison. Both analyses showed significant SNPs in regions on chromosomes 18 and 27. Putative top candidate genes from these regions included DLA-79, WNT10B, LMBR1L, KMT2D, and CCNT1. [ABSTRACT FROM AUTHOR]

Background: Lymphomas are dogs' most common hematopoietic neoplasms and represent a heterogeneous group, as occurs in humans. Considering the role of dogs as models of human lymphomas and the geographical correlation of the cases of canine and human lymphoma, it is important to continuously assess the epidemiological distribution of lymphoma subtypes in dogs. Aim: This study aimed to provide a survey of canine lymphoma subtypes diagnosed from 2005 to 2016 in the academic veterinary pathology laboratory of the University of Porto. Methods: A total of 75 canine lymphomas diagnosed by histopathology in the Porto district were included. All cases were immunophenotyped by CD3 and PAX5, classified according to the current classification WHO and coded with Vet-ICD-O-canine-1. Results: Mixed breed dogs were most common (28%), followed by Cocker Spaniels (12%), Boxers (9%), and Labrador Retrievers (6%). The mean age was 9.2 years (SD = 3.3) (10.7 years for small, 8.9 years for medium and large, and 5.7 years for giant breed dogs, p < 0.05). Regarding sex, there was no difference in frequencies or mean age. B-cell lymphomas were more common (57.4%) than T-cell lymphomas (37.3%), and 5.3% were classified as non-B/non-T-cell lymphomas. Of the cases, 49% had a multicentric distribution, followed by splenic (22%), cutaneous (12%), alimentary (12%), and extranodal (3%) forms. The most common B-cell subtypes were diffuse large B-cell lymphoma (DLBCL) (16.3%) and large immunoblastic lymphoma (14%), while T-zone lymphoma (21.4%) and intestinal lymphoma (18%) were the most common T-cell lymphoma subtypes. Conclusion: Our study shows that the Porto district follows the international trend of higher prevalence of B-cell lymphomas in dogs, especially of the DLBCL subtype. [ABSTRACT FROM AUTHOR]

Simple Summary: The development of a widely accepted and comparable animal cancer registration system lacks standardized animal cancer coding. The GIVCS group have developed a comparative coding system for canine neoplasms—Vet-ICD-O-canine-1—compatible with the human ICD-O-3.2 and consistent with the currently recognized classification schemes for canine tumors. This system comprises 335 topography codes and 534 morphology codes allowing the collection of consistent epidemiologic canine cancer data and offering a robust framework for comparative oncology studies. Cancer registries are fundamental tools for collecting epidemiological cancer data and developing cancer prevention and control strategies. While cancer registration is common in the human medical field, many attempts to develop animal cancer registries have been launched over time, but most have been discontinued. A pivotal aspect of cancer registration is the availability of cancer coding systems, as provided by the International Classification of Diseases for Oncology (ICD-O). Within the Global Initiative for Veterinary Cancer Surveillance (GIVCS), established to foster and coordinate animal cancer registration worldwide, a group of veterinary pathologists and epidemiologists developed a comparative coding system for canine neoplasms. Vet-ICD-O-canine-1 is compatible with the human ICD-O-3.2 and is consistent with the currently recognized classification schemes for canine tumors. It comprises 335 topography codes and 534 morphology codes. The same code as in ICD-O-3.2 was used for the majority of canine tumors showing a high level of similarity to their human counterparts (n = 408). De novo codes (n = 152) were created for specific canine tumor entities (n = 126) and topographic sites (n = 26). The Vet-ICD-O-canine-1 coding system represents a user-friendly, easily accessible, and comprehensive resource for developing a canine cancer registration system that will enable studies within the One Health space. [ABSTRACT FROM AUTHOR]