8180 Rare Variants Of Adrenocortical Carcinoma: A Retrospective Cohort Study

Abstract Disclosure: C.A. Villavicencio Torres: None. I. Bancos: None. Background: Adrenocortical carcinoma (ACC) is a rare malignancy with an estimated annual incidence of 0.7-2 cases per million per year. Scarce data are available on rare histological variants of ACC. Objective: To describe the clinical presentation and outcomes of patients diagnosed with oncocytic, sarcomatoid and myxoid ACC variants. Methods: Retrospective single center cohort study, 1992-2021 of patients with rare histological ACC variant. Results: A total of 20 patients were diagnosed with oncocytic (17, 85%), sarcomatoid (2, 10%), or myxoid (1, 5%) ACC. Median age of diagnosis was 47 years (range 17-80), and 14 (70%) were women. All patients had unilateral ACC (12, 60% left) with a median tumor size of 11 cm (range 4-29). Adrenal hormone excess was documented in 10 (50%) patients, mostly with either glucocorticoid or androgen excess. ENSAT stage I, II, III, and IV was documented in 2 (10%), 10 (50%), 6 (30%), and 2 (10%) patients, respectively. All patients were treated with adrenalectomy (laparoscopic in 5 and open in 15). In addition, patients were treated with mitotane (10, 50%), radiation (7, 35%), and chemotherapy (5,25%). Mitotane was administered for a median of 12 months (range 4-31) and was discontinued mainly due to side effects in 9 (90%) patients. Patients were followed for a median follow up of 6.5 years (range 0.4-12). In addition to 2 patients who presented with ENSAT stage IV metastatic disease, metastatic disease developed in additional 6 (30%) patients who initially presented with localized ACC (3 stage 2, 3 stage 3, 5 oncocytic, 1 sarcomatoid). Metastatic sites included lung (n=2), omentum (n=1), duodenum (n=1), liver (n=4), and bones (n=1). At the end of follow up, 11 (55%) patients remained disease free (53% oncocytic, 50% sarcomatoid, 100% myxoid), 5 (25%) patients were alive with metastatic ACC (23% oncocytic, 50% sarcomatoid), and 4 patients died of ACC (median time to death 21 months (range 10-50) post-adrenalectomy). Conclusions: Patients with oncocytic, sarcomatoid, and myxoid ACC may have a better prognosis than in reported literature. Larger multicenter studies are needed to identify patient and tumor-specific factors that guide management to assure improved outcomes in these very rare patients. Presentation: 6/2/2024