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Characterization of a tumour entity is based on the precise histopathological diagnosis taking into account the signalment of the diseased animal. The present study is a comprehensive, up-to-date statistical investigation on the type, frequency and breed distribution of neoplasia in dogs in Germany. The histopathological datasets of 109,616 German canine tissue samples (2014-2019) were processed and statistically examined in retrospect. Non-neoplastic diseases were found in 38,650 samples (35.3%) and 70,966 neoplasms (64.7%) were diagnosed. The most common neoplasms were mammary tumours (21.9%), benign epithelial skin tumours (15.4%), mast cell tumour (9.7%), histiocytoma (7.0%), soft tissue sarcoma (5.8%), lipoma (5.8%), melanocytic tumours (5.2%) and odontogenic tumours (4.7%). In general, Beagles, Magyar Vizslas, Boxers, Schnauzers, Spaniels, French Bulldogs and Golden Retrievers had an increased risk of neoplasia (odds ratio 1.17-1.46; all: P ≤0.001) compared with crossbreed dogs. In particular, Boxers, Golden Retrievers, Rottweilers and Schnauzers were often affected by malignant neoplasms, whereas some breeds (eg, West Highland White Terrier, Magyar Vizsla, Chihuahua, Dachshund and Yorkshire Terrier) were frequently affected by numerous benign tumour types. Despite the known risk of haemangiosarcoma in German Shepherd Dogs, other malignant tumours were rare in this breed. Depending on the type of tumour, some purebred dog breeds can have an increased, reduced or identical risk for certain neoplasms compared with crossbreeds. Discussion of breed predispositions to tumour diseases must therefore be conducted critically and with a view to clinical relevance.

Summary Although atrial dilation is a common finding in feline cardiac disease, detailed investigations of atrial pathology are rare in cats. The aim of the study was to investigate the correlation between pathohistological findings, morphometric data and the degree of dilation of the left atrial appendage (LAA) in 53 cats. Based on the LAA volume, the samples were grouped into normal/control (group 0, ≤1 ml [n = 9]), mildly dilated (group 1, >1 to ≤2 ml [n = 16]), moderately dilated (group 2, >2 to ≤3 ml [n = 14]) and markedly dilated (group 3, >3 ml [n = 14]) groups, independent of the underlying disease. Samples from the LAA and the left atrium (LA) were histologically evaluated using haematoxylin and eosin- and Picrosirius red-stained sections, and morphometrically analysed using an image analysis system. The degree of endo-, myo- and epicardial fibrosis was directly correlated with increased LAA dilation. Due to cardiomyocyte hyperplasia and hypertrophy, the mean thickness of the atrial wall was significantly greater in groups 1 and 2 than in group 0. Conversely, group 3 had a lower mean atrial wall thickness than groups 1 and 2, which was attributed to increased transmural fibrosis and cardiomyocyte atrophy. These findings reflect intensive dynamic remodelling processes during LA and LAA dilation, indicating that reversibility appears to be limited in cases of severe left atrial dilation.