Primary pulmonary adenocarcinoma metastasized to kidney in a captive nutria (Myocastor coypus)

A six-year-old male captive nutria (Myocastor coypus) maintained in a closed space with a small vent was found dead in his cage. Gross findings showed multifocal nodules in varying sizes, small 0.5 to large 5 cm in diameter, intermixed with normal parenchyma were scattered all over the surface of the lungs and a kidney, which the cut surface was smooth, compact and whitish in color. Microscopically, small round to oval neoplastic cells with modest to slight amounts of cytoplasm formed acinar and gland-like structures. Immunohistochemically, cells were strongly positive for E-cadherin and slightly reactive for thyroid transcription factor-1 (TTF-1). Based on those diagnostic features, the neoplasia was diagnosed as primary pulmonary adenocarcinoma (small cell type) and metastasized into the kidney. This is the first case report of malignant pulmonary tumor and its metastasis in the nutria.