Poorly differentiated neuroendocrine tumor and vertebral anomalies in a stranded Franciscana dolphin Pontoporia blainvillei

The Franciscana dolphin Pontoporia blainvillei is one of the most endangered cetaceans in the South Atlantic Ocean, primarily threatened due to bycatch. Knowledge regarding the natural causes of mortality and morbidity in this species is still limited. An adult female P. blainvillei that died as a result of bycatch was found stranded on the north coast of São Paulo, Brazil. At necropsy, a multi-cavitary tumor (~10.8 × 10.1 cm, 431 g) was found on the left adrenal gland, and on cut section, the tumor was hemorrhagic and necrotic. On histopathology, the tumor presented anaplastic characteristics including moderate anisocytosis and anisokaryosis, homogeneous and finely stippled chromatin, and nucleoli sometimes evident. Occasional binucleations and atypical giant cells were observed. The tumor was immunoreactive for chromogranin A and negative/not immunoreactive for Factor VIII, CD31, pan-cytokeratin AE1/AE3, vimentin, CD56, and synaptophysin, suggesting a poorly differentiated neuroendocrine tumor (NET). A moderate deviation of the lumbar spine (lordosis), lumbar ankylosing spondylosis, and thoracolumbar and caudal spine discopathy were confirmed via post-mortem radiographs. The vertebral anomalies and NET contribute to the knowledge of natural diseases of this endangered dolphin species.