Introduction An analysis of samples originating from domestic and exotic animals from Lower Silesia but also from other parts of Poland was carried out based on research conducted in 2014–2017. Material and Methods The materials used for the study were 11,338 tumour samples taken in vivo during surgery and as biopsies and posthumously during necropsies. They were sent to the Department of Pathology at Wrocław University of Environmental and Life Sciences for histopathological diagnosis. Results The largest group were canine tumours, of which there were 9,745 (85.95%), followed by feline tumours, totalling 1,397 (12.32%), tumours from exotic animals (186; 1.64%), from horses (7; 0.06%), and from cows (2; 0.02%). A significant number of cases of animals suffering from more than one tumour were also found, which had not been frequently diagnosed previously. Conclusion The number of neoplasms diagnosed in pets and exotic animals is increasing every year. The average animal age at diagnosis continues to fall. The greatest number of neoplasms were diagnosed in mixed-breed dogs and cats, and the number of tumours in a pure breed strictly correlated with breed’s popularity in the research period. Mesenchymal tumours are still the most prevalent type of tumours in dogs, while in cats epithelial tumours predominate. The neoplasm case pattern in animals conforms to that in humans in the same area.

A pet rabbit (female, 8 years old, and mixed breed) with symptoms of dyspnea, apathy, and weight loss was treated for an acute respiratory infection. Due to the lack of improvement, it was referred to the Imaging Diagnostics Laboratory of the Department and Clinic of Surgery for a computer tomography scan of the thoracic cavity. The examination revealed the presence of air in the pericardial sac, a pneumopericardium, along with pulmonary emphysema. A few minutes after the examination, the rabbit developed circulatory and respiratory failure and died. Necropsy confirmed the presence of a pneumopericardium and pulmonary emphysema, and revealed, in the tracheal lumen, the presence of a tumor histologically consistent with hemangioma. A spontaneous pneumopericardium occurs when air from the respiratory system moves into the pericardial sac. This is the first case of the simultaneous occurrence of tracheal hemangioma and a pneumopericardium in a rabbit.