Immunohistochemistry confirms pulmonary metastases from an adrenal adenocarcinoma causing primary hyperaldosteronism in a cat.

CASE SUMMARY: This report describes a 14-year-and-9-month-old, male neutered cat with a primary adrenal tumour secreting aldosterone with pulmonary metastases, alongside concurrent hyperthyroidism and congestive heart failure. The cat presented with hyporexia and muscular weakness, including marked cervical ventroflexion. Hypokalaemia, hypertension, marked hyperaldosteronaemia and presence of a left-sided adrenal mass were consistent with primary hyperaldosteronism, and pulmonary nodules were detectable radiographically. Congestive heart failure and poor quality of life resulted in euthanasia. Microscopic examination identified an adrenocortical carcinoma, and the histological morphology and immunohistochemical labelling was similar between the primary tumour and pulmonary nodules.

RELEVANCE AND NOVEL INFORMATION: Primary hyperaldosteronism is an underdiagnosed condition of cats, causing hypertension and hypokalaemia. Excessive aldosterone is secreted by the adrenal glands and may be caused by tumours. Around half of aldosterone-secreting tumours in cats are malignant, although distant metastases have only been reported once previously. This is the first report of radiographically evident pulmonary metastases from an aldosterone-secreting adrenal tumour confirmed by immunohistochemical labelling.