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Abstract Marine pollution, overrepresented by plastic, is a growing concern worldwide. However, there is little knowledge on occurrence and detrimental impacts of marine debris in cetaceans. To partially fill in this gap of knowledge, we aimed to investigate the occurrence and pathologies associated with foreign bodies (FBs) in a large cohort of cetaceans (n = 465) stranded in the Canary Islands. The Canary Islands shelter the greatest cetacean biodiversity in Europe, with up to 30 different species, of which nine are regularly present year around. We found at least one ingested FB in 36 out of 465 (7.74%) studied cetaceans, involving 15 different species, including eight out of the nine (80%) cetacean species present year-round in the Canary Islands. Risso's dolphin was the species most affected, followed by sperm whale, beaked whale and mysticetes. Plastic FB were the most common item found (80.56%). FB was directly associated with death in 13/36 (36.11%) animals. Poor body condition and deep diving behavior were found to be risk factors for FB ingestion, whereas the adult age was a protective factor. To the authors knowledge this is the first study that use statistical analysis to investigate risk and protective factors for FB ingestion. This study also provides insights of the potential impact caused by ingested FBs on the animal's health and mortality. This knowledge is critical to better understand and assess the impact of FB in cetaceans setting the scientific basis for prospective impact monitoring and future conservation policies. Graphical abstract Image 1 Highlights • Foreign bodies were found in 7.7% (36/465) studied cetaceans in the Canary Islands in a 16 year period. • Severe digestive disease (impactions and gastrointestinal perforations) caused the death of 13 animals (2.8%,13/465). • Plastic was the most common item found (80.6%). • Poor body condition and deep diving behavior were risk factors for foreign body ingestion. • Adult age was a protective factor for foreign body ingestion. This manuscript contributes to increase the current understanding of the epidemiology and pathology of foreign bodies in cetaceans and provides a scientific foundation for conservation policies. [ABSTRACT FROM AUTHOR]

Summary This report describes the histological and immunohistochemical features of multicentric, benign, epithelial inclusions (BEIs) in a free-ranging, adult, female Risso's dolphin ( Grampus griseus ). The differential diagnoses included ectopic hamartomatous epithelial inclusions, non-Müllerian choristoma, Müllerian choristoma and low-grade metastatic carcinoma/mesothelioma. The most likely diagnosis of such BEIs was multicentric, embolic, reactive mesothelium, as suggested by cytomorphological and immunophenotypical features of the BEIs, the occurrence of focal pleural rupture and the immunophenotype of the pleural mesothelium. The former represents a pathological condition not previously reported in a marine mammal species, rarely described in animals, and relatively infrequently recognized in man. [ABSTRACT FROM AUTHOR]

Summary A uterine prolapse associated with a leiomyoma (fibroid) was observed in a live-stranded Atlantic spotted dolphin ( Stenella frontalis ). A 7 cm segment of the reproductive tract including the cervix, uterine neck and caudal uterine body had intussuscepted and prolapsed into the cranial vaginal vault. In the leading edge of the intussuscepted/prolapsed uterine wall was a 6 × 3 × 3.5 cm leiomyoma expanding the myometrium. The leiomyoma and prolapse were associated with necrotizing exposure endometritis. This is the first report of a uterine prolapse associated with a leiomyoma in a cetacean. This lesion was believed to be the underlying cause of the live stranding. [ABSTRACT FROM AUTHOR]

Summary This report describes the gross, microscopical and immunohistochemical features of a high-grade astrocytoma (glioblastoma multiforme) in an adult male Atlantic spotted dolphin ( Stenella frontalis ). On necropsy examination, a 5 × 2.5 × 2 cm, poorly demarcated, red, friable and locally expansile mass effaced the thalamus and the left periventricular region and extended to the left lateral ventricle of the brain. Microscopically, the mass consisted of haphazardly arranged bundles and rows of interweaving polygonal to spindle-shaped cells. These often palisaded along serpentine foci of necrosis and were surrounded by prominent vessels. Immunohistochemically, the neoplastic cells expressed glial fibrillary acidic protein, but not vimentin, S100 protein, neuron-specific enolase or neurofilament protein. A diagnosis of high-grade astrocytoma was made and this represents the first description of a glioma in a cetacean species. [ABSTRACT FROM AUTHOR]

Summary: This report describes the pathological findings in an adult female short-beaked common dolphin (Delphinus delphis) stranded alive in the Canary Islands. Necropsy examination revealed the presence of a nodular neoplastic growth in the central nervous system (CNS) at the level of the thalamus. Microscopical examination revealed the mass to be a lymphoma and immunohistochemical labelling demonstrated a T-cell origin. No significant lesions were observed in other organs, including lymphoid organs. This is the first report of a primary T-cell lymphoma in the CNS in cetaceans. [ABSTRACT FROM AUTHOR]

Summary: The cross-reactivity of monoclonal antibodies specific for human, porcine and bovine cytokines was evaluated for three cetacean species: Atlantic spotted dolphins (Stenella frontalis), striped dolphins (Stenella coeruleoalba) and fin whales (Balaenoptera physalus). Formalin-fixed and snap-frozen tissue sections of lung, spleen, liver and mesenteric lymph node were evaluated. T and B lymphocytes and monocytes/macrophages were detected by use of anti-human CD3, IgG and lysozyme polyclonal antibodies (pAbs), respectively. These reagents were successfully applied to both fixed and frozen tissues. Anti-human interleukin (IL)-1α, IL-1β, IL-8, tumour necrosis factor (TNF)-α and CD25, anti-porcine IL-2, IL-6, IL-10, and anti-bovine IL-4 and interferon (IFN)-γ antibodies produced immunolabelling in cetacean snap-frozen lymph node sections similar to that obtained with tissue from the species of origin, but they did not react with formalin-fixed tissue sections. Anti-porcine IL-12 pAb did not react with snap-frozen cetacean tissue samples. Macrophages and lymphocytes were the most common cells immunolabelled with the anti-cytokine antibodies. This panel of anti-cytokine antibodies may be used to evaluate cytokine expression in snap-frozen tissue samples from the cetacean species tested. [Copyright &y& Elsevier]

Summary: This report describes a large cell immunoblastic lymphoma in a bottlenose dolphin found stranded alive in Gran Canaria, Spain. Diffuse infiltration of round neoplastic cells was observed in the splenic cords and sinuses and in hepatic sinusoids, resulting in moderate organ enlargement. The tumour cells (immunophenotype IgG+ and CD3−) showed scant, lightly eosinophilic or basophilic cytoplasm, distinct cell boundaries and hyperchromatic nuclei, each with one or more nucleoli. Mitoses were common. On the basis of histopathological, immunohistochemical and ultrastructural features, the tumour was classified as an immunoblastic lymphoma. Eleven polychlorinated biphenyl (PCB) congeners, 23 organochlorine pesticides and 16 polycyclic aromatic hydrocarbons (PAHs) were detected in the blubber and liver. High concentrations of PCBs 153, 180, 138 and 187 found in the liver may have been associated with the hepatosplenic lymphoma. [Copyright &y& Elsevier]