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Background: Lung cancer is the most commonly diagnosed neoplasm in humans, however this does not apply to other animal species. Living in an aquatic environment the respiratory system of cetaceans had to undergo unique adaptations in order to them to survive and cope with totally different respiratory pathogens and potentially carcinogens from those affecting humans. Case presentation: This article discusses not only macroscopical, histopathological and immunohistochemical features of a pulmonary carcinoma with disseminated metastases in a long-finned pilot whale (Globicephala melas), as well as the immunohistochemical analysis performed on various tissues of cetaceans belonging to the genus Globicephala. On the necropsy examination of the carcass, multiple pulmonary nodules and generalised thoracic lymphadenomegaly were noted. Histologically, a malignant epithelial neoplasia was identified in the lung, thoracic lymph nodes, and adrenal gland. Immunohistochemical analysis revealed a pulmonary carcinoma. Vasculogenic mimicry and epithelial-to-mesenchymal transition phenotype, as suggested by cytomorphological and immunohistochemical characteristics, were observed. Conclusions: A diagnosis of metastatic pulmonary carcinoma was determined, which to the author's knowledge, appears to be not previously recorded in long-finned pilot whale species. This is also the first report of vasculogenic mimicry and epithelial-to-mesenchymal transition event in a spontaneous cancer from a cetacean species. [ABSTRACT FROM AUTHOR]

Simple Summary: Characterization, description, and geographical location of harmful bacterial agents in cetaceans are important for population surveillance and health monitoring around the world. This research compiles the pathologic features of nocardiosis in five free-ranging delphinids from the Canary Islands and Andalusia. All examined animals showed a disseminated pattern of infection with characteristic suppurative to pyogranulomatous lesions with thromboembolism in two or more organs. The obtained results provide the first record of N. otitidiscaviarum in cetaceans, the first account of N. farcinica in free-ranging dolphins, and confirmation of nocardiosis in central eastern Atlantic Ocean. We report the pathologic features of nocardiosis in five free-ranging delphinids from the Canary Islands and Andalusia, namely four striped dolphins (Stenella coerulealba) and one bottlenose dolphin (Tursiops truncatus). All animals had a multiorgan (disseminated) pattern of infection involving suppurative to pyogranulomatous and thromboembolic lesions in two or more organs. Most affected organs were (by decreasing order) lung, pulmonary lymph nodes, liver, kidney, adrenal glands, and central nervous system. Typical intralesional and intravascular branched and filamentous bacteria were highlighted by Grocott's methenamine silver and Gram stains. Bacterial analysis including 16S rRNA gene sequencing identified Nocardia farcinica in two striped dolphins and Nocardia otitidiscaviarum in one striped dolphin and the bottlenose dolphin. All dolphins tested (n = 4) for cetacean morbillivirus were negative; one dolphin had concurrent cutaneous herpesvirosis. These results provide the first record of N. otitidiscaviarum in cetaceans, the first account of N. farcinica in free-ranging dolphins, and confirmation of nocardiosis in central eastern Atlantic Ocean. These results expand the known geographic range of nocardiosis in cetaceans. [ABSTRACT FROM AUTHOR]