SUN-160 Development of Adrenocortical Carcinoma in an Adrenal Nodule After Nine Years of Size Stability on Imaging: A Case for Critical Review of Efficacy of Radiographic Size Criteria

BACKGROUND: Current consensus guidelines for adrenal incidentalomas smaller than 4 cm recommend re-evaluation up to 2 years. Although there is no consensus for imaging surveillance beyond 2 years, in general, stability in size over time is considered a sign of benign nature. Clinical Case: A 50-year-old African-American woman presented to Endocrinology for resistant hypertension since age 30 and an enlarging right adrenal nodule. She was obese, weighing 138.8 kg with a BMI of 55.97 kg/m(2), without clinical Cushingoid features. At her first visit she was taking the following antihypertensives: amlodipine, losartan, hydrochlorothiazide, and clonidine patch. She took no other prescription medications. Her baseline metabolic blood profile was normal. Further testing revealed a profile consistent with possible primary hyperaldosteronism and subclinical Cushing’s syndrome: plasma aldosterone 17 ng/dl, plasma renin activity 0.232 ng/ml/hour, ACTH 10 pg/ml, AM cortisol 8.3 mcg/dl, DHEAS 30 mcg/dl, and 1mg dexamethasone suppression test resulted in cortisol of 7.6 mcg/dl (normal < 1.8 mcg /dl) with a simultaneous dexamethasone level of 357 ng/dl (140 – 295 ng/dl). However, 24-hour urinary free cortisol and urinary metanephrines were within reference ranges. Further confirmatory tests were not performed due to her imaging findings, as described below. The earliest abdominal imaging was a CT abdomen with contrast in 2005 which measured a 2.1 cm right adrenal mass. For various reasons she had repeat CT contrast imaging in 2006, 2007, 2012, and 2014 demonstrating no changes in the dimensions of her adrenal nodule, noting all the studies were performed with contrast only and without Hounsfield unit (HU) measurements. In 2017, a CT abdomen with adrenal protocol demonstrated a right adrenal mass measuring 4 cm x 3.5 cm (increased from 2.1 X 1.2 cm in 2014), characterized by 43 HU pre-contrast, 71 HU post-contrast, and an absolute washout of 29%. Due to high suspicion for malignancy, a PET-CT was performed with FDG, which revealed high uptake in the right adrenal mass. She was referred for a right adrenalectomy and pathology showed adrenocortical carcinoma with some infiltration into adipose tissue. There was a high mitotic index (42 per 50 high powered fields) and Ki67 of 35%, classified as Stage III pT3NxM0. She was referred to oncology and treated with external radiation to the adrenal bed along with initiation of mitotane. Conclusion: This case infers that long-term size stability of an adrenal nodule does not confer full confidence of a benign process. Compared with previous reports in the literature describing long latencies for ACC, this is one of the longest records of size stability over 9 years followed by a size increase 3 years later.