Concurrent adrenal myelolipoma and functional corticomedullary mixed tumour in a dog with Cushing's syndrome

Abstract A 12‐year‐old, female dog presented with polyuria, polydipsia and an adrenal mass. Diagnostic imaging and endocrine tests yielded inconclusive results, displaying characteristics of both adrenocortical and medullary neoplasms. Surgical excision, postponed by 3 months, revealed a markedly enlarged tumour necessitating concurrent nephrectomy. Histopathological examination and immunohistochemical analysis confirmed a rare mixed corticomedullary tumour with an associated myelolipoma. The dog exhibited a favourable post‐surgical outcome, with resolution of clinical signs and no evidence of recurrence or metastasis at the 10‐month follow‐up. This case underscores the diagnostic challenges posed by complex adrenal tumours and emphasises the crucial role of immunohistochemistry in achieving accurate characterisation, particularly when clinical and imaging findings are discordant. Heightened awareness of unusual entities, such as mixed adrenal tumours and concomitant myelolipomas, is essential for ensuring appropriate diagnosis and management in similar cases.