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  • An approximately 11-year-old, 11.8-kg spayed female Terrier-mixed-breed canine presented to her primary care veterinarian for a routine dental exam and had pre-operative bloodwork. On bloodwork, there was increased Alkaline Phosphatase (860 U/L; reference range, 20 to 150 U/L), a mild hypercalcemia (12.5 mg/dL; reference range, 8.6 to 11.8 mg/dL) accompanied by a mild hyperalbuminemia (5.0 g/dL; reference range, 2.5 to 4.4 mg/dL), and moderate hemoconcentration (65.43 %; reference range, 37 to 55.0 %). Further investigation was recommended to evaluate the elevated liver enzyme and signs of hyperadrenocorticism.
  • An abdominal ultrasound, ACTH stimulation test, and ionized calcium was performed prior to referral.
    • The ionized calcium was normal (1.36 mmol/L; reference range, 1.24 to 1.43 mmol/L).
    • ACTH stimulation test results were elevated, demonstrating hypercortisolism, but not definitive for hyperadrenocorticism (Pre-ACTH Cortisol 12.8 ug/dL; reference range, 1.0 to 5.0 ug/dL; Post-ACTH Cortisol 19.8 ug/dL; reference range, 8.0 to 17.0 ug/dL).
    • Abdominal ultrasound was performed prior to specialty referral which seems to suggest that there is a mass by the region of the left adrenal gland that was in contact with the left renal vein. The caudal vena cava was not evaluated on that ultrasound.
  • The owner was interested in pursuing further diagnostics and surgery and therefore the patient was referred to a specialty practice. On referral examination, the patient had mild tartar and dental disease, and an approximately 5cm by 5cm soft, subcutaneous, freely movable mass on the point of the left shoulder which was previously aspirated and consistent with a lipoma cytologically. The remainder of the examination was unremarkable.
  • A CT was recommended to further evaluate the abdominal mass and for surgical planning, if indicated.
  • The caudal pole of the left adrenal gland is enlarged by a 26x24x21mm, mixed hypoattenuating/fat (-40 – -80 HU) mass. Adrenal tissues is visualized along all margins of the mass. The mass contacts and caudally displaces the left renal vein. There is a fat attenuating plane separating the mass from the left kidney.
  • There is a scant volume of gas present within the right aspect of the heart, cranial vena cava and integral thoracic veins, secondary to IV drug and fluid administration. The heart is otherwise normal.
  • There is a mild increase in the attenuation of the dorsal lung lobes secondary to atelectasis, otherwise the pulmonary parenchyma is normal. The remaining intrathoracic structures are normal.
  • There is a mild volume of mineral attenuating material present with the gravity independent portion of the gallbladder. The liver and spleen are normal. The gastrointestinal tract and pancreas are normal. The kidneys and bladder are normal. The right adrenal gland is normal.
  • There is an oval, approximately 10mm, soft tissue attenuating nodule present in the right dorsal subcutaneous tissues, confluent with the dermis, in the region of the scapula, and a similar 6mm lesion in the region of the left scapula. There is a 60x30x40mm, homogenously fat attenuating mass present in the left triceps muscle.
  • Fat attenuating mass arising from the left adrenal gland has differentials of benign, myelolipoma or lipoma and less likely a liposarcoma
  • Incidental findings:
    • Adhered cholelithiasis vs mineralization of the gallbladder wal
    • Subcutaneous dermal granulomas vs neoplasia – Left triceps intramuscular lipoma

The patient was taken to surgery for a left adrenalectomy.

Histopathology results for the adrenal gland show evidence of an adrenocortical adenoma with a central mass composed almost entirely of adipocytes.

A liver biopsy was also taken showing moderate diffuse vacuolar hepatopathy. The patient is since doing well. There is no new information currently in terms of the patient’s hypercortisolism status

This case shows the diagnostic work-up of a patient with an incidental finding of an adrenal mass and hypercortisolism. Adrenal masses in dogs can be functional or non-functional, and can arise from the cortex, the medulla, or as metastatic spread. Common differentials for adrenal masses are adenoma, carcinoma, and pheochromocytoma. (1,2) In the case of this patient, the mass had a component of an adrenocortical adenoma, but in addition it had a myelolipomatous center which was adding to the size of the mass. Adrenal myelolipomas are benign, endocrinologically inactive tumors that are uncommonly found in dogs. (3) There have been sporadic reports of adrenal myelolipomas in dogs where their imaging characteristics have been described. (1,3,4). On Computed Tomography (CT), these masses have been reported to have a fat attenuating center with a soft-tissue attenuating and contrast enhancing rim, as seen in this patient. (1,4) It is known that, for the overwhelming majority of adrenal masses, there is no reliable diagnostics characteristics to differentiate between underlying pathologies with imaging alone, and additional testing is generally recommended. (1,2,5). We believe, however, that due to the unique appearance and fat attenuating center of these masses on CT, it is possible to more confidently be able to recognize and differentiate adrenal myelolipomas from other adrenal masses. Regardless, future studies are needed to better understand the statistical significance of the association between CT features and histological findings of adrenal myelolipomas. Additionally, because this particular case had evidence of a functional disease component to the mass, it would be appropriate to have further testing for evaluating hypercortisolism status post-surgical removal; a repeat ACTH Stimulation using the same testing facility would be the most appropriate for a better comparison.

1. Schwarz, T., & Saunders, J. (2011). Veterinary Computed Tomography (1st ed.). Wiley-Blackwell.

2. Mattoon, J. S., Sellon, R. K., & Berry, C. R. (2020). Small Animal Diagnostic Ultrasound, 4e (4th ed.). Saunders.

3. Tursi, M., Iussich, S., Prunotto, M., & Buracco, P. (2005). Adrenal Myelolipoma in a Dog. Veterinary Pathology, 42(2), 232–235. https://doi.org/10.1354/vp.42-2-232

4. MORANDI, F., MAYS, J. L., NEWMAN, S. J., & ADAMS, W. H. (2007). IMAGING DIAGNOSIS-BILATERAL ADRENAL ADENOMAS AND MYELOLIPOMAS IN A DOG. Veterinary Radiology & Ultrasound, 48(3), 246–249. https://doi.org/10.1111/j.1740-8261.2007.00237.x

5. Bokhorst, K. L., Kooistra, H. S., Boroffka, S. A., & Galac, S. (2018). Concurrent pituitary and adrenocortical lesions on computed tomography imaging in dogs with spontaneous hypercortisolism. Journal of Veterinary Internal Medicine. https://doi.org/10.1111/jvim.15378

Left Adrenal post-op pictures: Mass removed at the location of the left adrenal mass. Size measurement of the adrenal mass after surgical removal (A). Cut section of the adrenal mass (B). Lipomatous center causing distention of normal adrenal shape and structure.

Histopathology picture: The adrenal mass is an adrenocortical adenoma. This mass includes myelolipomatous change that is prominent in the central aspect.