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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]

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]