Primary adrenal lymphoma causing hypoaldosteronism in a cat

CASE SUMMARY A 10-year-old, 5.1 kg (11.2 lb), male castrated cat was presented with signs of lethargy and decreased appetite at home after being previously healthy. Serum biochemical analysis identified normokalemia (5.1 mmol/l; reference interval [RI] 3.4-5.6 mmol/l) and severe hyponatremia (123 mmol/l; RI 145-158 mmol/l), with an Na/K ratio of 24 (RI 32-41). Baseline serum cortisol was low to normal, but serum aldosterone was markedly decreased with a pre-adrenocorticotropic hormone stimulation concentration of 13 pmol/l (RI 194-388 pmol/l) and post-adrenocorticotropic hormone stimulation concentration of 21 pmol/l (RI 277-721 pmol/l). Hematologic and biochemical analyses were otherwise unremarkable. Abdominal ultrasound revealed bilaterally enlarged adrenal glands with no other abnormalities noted; thoracic radiographs also did not identify any signs of metastasis. Fine-needle aspiration was strongly suggestive of lymphoma of the adrenal glands, and PCR for antigen receptor rearrangement was positive for B-cell clonal expansion; based on these findings, a diagnosis of primary adrenal B-cell lymphoma was made. Stable disease was achieved for a short period of time following vincristine, cyclophosphamide, prednisolone and fludrocortisone therapy, followed by progressive adrenal enlargement and electrolyte derangements that responded to neither doxorubicin nor adjustments in fludrocortisone dosage. Ultrasonographic metastasis was not identified at any time, and other organ derangements were not noted on hematologic or biochemical analyses. The cat was euthanized 55 days after initial presentation. RELEVANCE AND NOVEL INFORMATION This is the first report of primary adrenal lymphoma in a cat, with presenting signs compatible with hypoaldosteronism. Lymphoma should be a differential for cats presenting with adrenal enlargement or clinical signs and biochemical changes consistent with hypoaldosteronism or hypoadrenocorticism.