SUN-378 Adrenocortical Carcinoma Diagnosed During Evaluation of an Incidentally Discovered Adrenal Mass

Background. Adrenocortical carcinoma (ACC) is a rare neoplasm with an estimated incidence of 0.5-2.0 per million per year. Most patients present with symptoms or signs of hormone excess or complaints related to tumor mass effect. We present a case of ACC discovered incidentally on computed tomography (CT) imaging of the abdomen. Case. A 59-year-old female presented to the emergency department (ED) after falling in her shower. She felt light headed before the fall, but she denied loss of consciousness or confusion after the event. The patient was noted to be hypertensive (185/105 mm Hg) and hypokalemic (2.6 mM, 3.6-5.1). A contrast enhanced abdominal CT scan revealed a 9.1 cm heterogeneous left adrenal mass. Plasma metanephrine and normetanephrine levels were unremarkable. Morning cortisol failed to suppress during a 1 mg overnight dexamethasone suppression test (10.1 μg/dL, < 1.8), and plasma midnight cortisol was unequivocally elevated at 24.3 μg/dL (< 7.5). ACTH (5 pg/mL, 6-58) and DHEA (0.159 ng/mL, 0.630-4.700) levels at 8 AM were both low. Postsurgical histopathology was notable for high grade mitoses (> 20/50 high powered fields), capsular invasion into peri-adrenal adipose tissue, and lymphovascular invasion, though surgical margins were uninvolved by tumor. No evidence of locoregional or distant metastases was observed on tumor staging, leading to a diagnosis of stage III ACC (T3N0M0). The patient elected treatment with local external beam radiation but declined mitotane. Secondary adrenal insufficiency is managed with hydrocortisone. Discussion. This patient’s case illustrates the female predominance (1.5-2.5:1) and typical time of diagnosis (fifth-to-sixth decade) reported in adult cases of ACC. It is unusual because only 20-30% of cases are diagnosed incidentally during imaging for an unrelated medical problem, and ACC accounts for only about 2-5% of incidentally diagnosed adrenal masses. The size (> 4 cm) and heterogeneity of the patient’s tumor were radiographic features indicating ACC, and the finding of adrenal hypercortisolemia is consistent with the high prevalence (45-70%) of metabolically active tumors that predominantly secrete cortisol. Hypertension and hypokalemia likely reflect saturation of renal 11-β-hydroxysteroid dehydrogenase with excess cortisol, though the patient lacked the features of rapidly progressive Cushing’s syndrome described in many cases of cortisol secreting ACC. Most cases of ACC are stage II or higher at initial diagnosis, and five-year survival for advanced stage ACC is only 10-25%. Disease stage and completeness of resection are the most important factors that influence prognosis, though high mitotic rate and hypercortisolemia in this patient’s case are negative prognostic factors. Adjuvant mitotane appears to improve recurrence-free survival, and radiation reduces the rate of local tumor recurrence.