Case Study

Pheochromocytoma and adrenocortical carcinoma in an 11 year old FS Labrador Retriever mix

An 11-year-old FS Labrador mixed breed dog presented for increased thirst. In-house blood chemistry revealed hyperphosphatemia and high cholesterol. CBC found only high HGB. Urinalysis showed low specific gravity, trace proteinuria, and hematuria. Patient returned one month later for recheck exam. Owner reported polyuria and polydipsia. Physical examination found severe dry skin, clumped hair coat with alopecia in several areas, and a pot-bellied appearance (patient obese.) Neither low dose nor high dose dexamethasone suppression test showed suppression. ACTH stim was non-diagnostic.

DX

Pheochromocytoma and adrenocortical carcinoma

Sonographic Differential Diagnosis

Mineralizing right adrenal mass with slight caval invasion, suspect functional adenocarcinoma. Follow-up images reveal a nodule in the adjacent right caudal liver suspect for contiguous metastasis.

Image Interpretation

The left adrenal gland was subnormal in size and volume with flat contour (Image 1). The right adrenal however comprised a moderately echogenic mass measuring 5.8 x 3.5cm with focal areas of mineralization which was largely isoechoic to surrounding tissue (Image 2 and Videos 1 & 2). Color flow Doppler revealed deviation/mass effect upon the surrounding vasculature in the near field and overlay or invasion into the vena cava (3 o`clock position.) The vena cava approached from underneath the right adrenal mass in a right retrocostal position revealed no overt caval invasion in the visible field suggestive for potential resectability, ideally to be confirmed on CT evaluation (Video 3). Color flow of the adjacent vena cava help distinguish this largely isoechoic/hyperechoic hepatic nodule from surrounding fat and liver. This adrenal mass is most consistent with adrenal adenocarcinoma with possible hepatic metastatic disease. Small metastatic liver lesion seen at liver edge, just ventral to vena cava in this approach (Image 3). In a post surgical follow-up sonogram, the caudal aspect of the right liver revealed a mildly hypoechoic and slightly mixed echogenic 1.5 cm nodule adjacent to where the right adrenal mass was surgically removed (Video 4 and Image 4). The nodule appears in the last second of the video clip after sweeping through the right kidney.

Outcome

Patient was sent to referral hospital for CT scan and possibly surgery. CT scan showed 1-2 mm invasion in the vena cava and it was estimated 50:50 chance of survival with surgery. Patient went to surgery for adrenalectomy (right) and biopsy. Patient recovered uneventfully from surgery and at sutures out was doing very well. Patient was recommended for recheck ultrasound in six weeks and oncology consult. Follow-up surgery on the the liver nodule 9 months after the original surgery revealed metastatic adrenal carcinoma but remained focal. The patient recovered normally and was asymptomatic 6 months after the second surgery.

Clinical Differential Diagnosis

Hyperadrenocorticism caused by an adrenal tumor (adenoma or adenocarcinoma), an adrenal tumor causing the overproduction of sex hormones (atypical Cushing’s disease,) pheochromocytoma.

Sampling

Full-thickness surgical biopsy was completed. Results of biopsy discovered two tumors present. A small pheochromocytoma which was completely removed; the larger an adrenocortical carcinoma which had cells extending to the edge of section, giving a high chance of recurrence.