FRI178 The Clinicopathological Distinction And Malignant Potential In Patients With Lipid-rich and Lipid-poor Non-functioning Adrenal Adenoma

Abstract Disclosure: P. Pengkhum: None. S. Lertlam: None. P. Cheunsuchon: None. V. Suvannarerg: None. S. Sirinvaravong: None. T. Wannachalee: None. Introduction: Adrenal incidentaloma (AI) is defined as an adrenal mass detected during imaging performed for conditions unrelated to suspected adrenal diseases. The latest evidence shows that most AIs are non-functioning adrenocortical adenomas (NFA). Of these, 70% are lipid-rich adenomas (LRA) and 30% are lipid-poor adenomas (LPA). Current guidelines do not recommend further follow-up imaging in patients with an adrenal mass size <4 cm with clear benign features. But some non-functioning lipid-poor lesions may carry malignant potential and proper management including surgical resection should be offered. However, the natural history and optimal specific follow-up surveillance of non-functioning LPA have not been well characterized. Objectives: We aimed to evaluate the clinical characteristics, natural courses, and histopathological data in NFA, and compared the malignant potential between LRA and LPA. Methods: We retrospectively studied all patients with AI between Jan 2005 to June 2022. Only patients with NFA who underwent adrenalectomy or were followed up by imaging for at least 6 months were included. The demographic, radiographic, and follow-up data were evaluated in all patients. Available adrenal tissues were performed for pathological assessment by using the Weiss score, Ki-67, and reticulin algorithm to identify the malignant potential. Results: Of 303 patients with AIs, 146 patients (48%) with NFAs were recruited, including 79 masses in LRA group and 77 masses in LPA group. Of these, the median age was 61 years, 43% were men, and the median follow-up period was 47 months. The initial median adenoma size was 1.6 cm [1.2-2.1]. During the follow-up period, only 3 LPAs developed significant interval enlargement. However, none of these were neither treated by surgical resection nor demonstrated malignant transformation based on imaging appearance. Overall, there was no difference in tumor growth between both groups by radiological assessment. Furthermore, 27 patients of NFAs underwent adrenalectomy; 8 masses in LRA group and 19 masses in LPA group. Of these, no difference in histological assessment in both groups. However, two large LPAs which size ≥4 cm revealed a Weiss score ≥3 with the presence of reticulin algorithm indicating potential malignant behavior. In contrast to LRA. Regardless of the adrenal mass size, the histopathological results revealed no suggestive malignant features. Conclusions: There was no significant difference in characteristics and tumor growth in patients with non-functioning LRA and LPA across 4-year interval follow-up data. Significant enlargement of adenomas was observed in few small LPAs, therefore periodic follow-up imaging should be offered in small LPAs with evidence of interval enlargement. According to our histopathological data, surgical resection should be considered in the large LPA (≥4 cm) due to its malignant potential. Presentation: Friday, June 16, 2023