Adrenal gland adenoma with myelolipoma in a canine patient: a rare case report and diagnostic insights.

Adrenal gland tumors are uncommon in dogs, and the simultaneous presence of epithelial and mesenchymal neoplasms within a single adrenal gland is exceptionally rare. We describe a rare case of an adrenocortical adenoma associated with a myelolipoma in a 7-year-old male Pekingese dog presented with acute abdominal pain and fever. Diagnostic imaging identified a well-defined mass in the right adrenal gland, with no evidence of vascular invasion or metastatic disease. Surgical adrenalectomy was subsequently performed. Histopathological evaluation revealed a well-circumscribed adrenocortical adenoma containing an intratumoral myelolipomatous component composed of mature adipose tissue and trilineage hematopoietic elements. Immunohistochemical analysis demonstrated Melan A positivity in the adenomatous component, while the myelolipomatous tissue showed diffuse vimentin expression and lacked Melan A immunoreactivity. The postoperative course was uneventful, and no recurrence was detected at one-year follow-up. This case underscores the diagnostic complexity of heterogeneous adrenal masses in dogs and highlights the essential role of histopathology and immunohistochemistry in the accurate identification of rare mixed adrenal lesions.