CEREBELLAR AND MESENCEPHALON NEOPLASIA IN A NILE HIPOPPOTAMUS (HIPPOPOTAMUS AMPHIBIOUS)

Area of Science:

• Veterinary Pathology
• Comparative Oncology
• Wildlife Health

Background:

• Adenocarcinomas can occur in various species, sometimes exhibiting unusual differentiation.
• Neuroendocrine differentiation in tumors can alter their behavior and clinical presentation.
• Hippopotamus (Hippopotamus amphibious) health is not extensively studied, especially regarding neoplastic diseases.

Purpose of the Study:

• To characterize a fatal neoplastic disease in a Nile hippopotamus.
• To investigate the cell of origin and differentiation of multiple masses.
• To compare findings with known tumor behavior in other species.

Main Methods:

• Necropsy and histopathological examination of a deceased Nile hippopotamus.
• Immunohistochemical analysis to confirm adenocarcinoma and assess differentiation.
• Gross examination of brain (cerebellum, mesencephalon) and adrenal gland masses.

Main Results:

• A 52-year-old female hippopotamus presented with progressive neurological signs and weakness.
• Three firm, tan masses were identified: two in the brain and one in the adrenal gland.
• Histopathology confirmed adenocarcinoma with neuroendocrine differentiation in the adrenal gland but not the brain.

Conclusions:

• The findings suggest either two distinct tumors or a single metastasizing adenocarcinoma with focal endocrine differentiation.
• The adrenal gland is a potential primary site, with small primary lesions possibly missed during gross examination.
• Further investigation is needed to determine the exact cell of origin and the implications of neuroendocrine differentiation in this species.