SAT-480 - Clinical Features of Adrenal Neoplasms of Uncertain Malignant Potential: A 25-Year Experience at a Tertiary Cancer Center

Background: Adrenal neoplasm of uncertain malignant potential (ANUMP) is an adrenocortical tumor that does not fully meet the criteria for malignancy but exhibits concerning histological features. Due to the rarity of this diagnosis, there is limited data about the clinical features and outcomes of ANUMPs. To address this knowledge gap, we evaluated the clinicopathological features of patients with ANUMP over a 25-year period at a tertiary cancer center.

Methods: We performed a retrospective chart review of surgically treated patients between 2000 and 2025 with identified ANUMP on pathology. Clinical, biochemical, and pathological data were extracted from medical records. Descriptive statistics were used to summarize the data.

Results: We identified 54 patients (38 women, 70%) with median age of 45 years (range 21-78). ANUMPs were discovered incidentally in 19 (35.2%), due to pain/mass effect in 18 (33.3%), clinical hormonal excess in 5 (9%), and an unknown presentation in 12 (22%). Median tumor size on imaging closest to surgery was 42 mm (range 15-270). Median follow-up was 32 months (range 0-388). Presurgical hormonal evaluation was available for 25 (46.2%) patients: cortisol excess in 3 (12%), androgen excess in 5 (20%), co-secretion of cortisol and androgen in 5 (20%), and hormonally silent in 12 (48%). All pathological specimens were reviewed by expert adrenal pathologist and reclassified as adrenal cortical neoplasm of uncertain malignant potential (ACNUMP) 23 (42.5%), oncocytic adrenal neoplasm of uncertain malignant potential (OANUMP) 22 (40.7), and adrenal neoplasms 9 (16.7%).None of the cases were classified as adrenal cortical carcinoma based on Weiss criteria after pathology review. Median Ki-67 was 5 (range 1-23) in 42 evaluable patients. At the time of data cutoff, 13 (24%) patients were lost to follow up, 35 (64.8%) were alive without disease, 2 patients (3.7%) died of other causes, and 4 (7.4%) had developed metastatic disease at 14,36,53,and 57 months. Among metastatic cases: two were functioning tumors at diagnosis; 3 had open resections; margins were R0 in 1, R2 in 1 and Rx in 2; median presurgical size was 80.5 mm (42-160); Ki67% ranged from 6.7-13% in three evaluable patients; and median time to metastasis was 44.5 months (range 14-57). After ANUMP diagnosis, 2 were alive with disease at 28 and 83 months whereas 2 had died of disease at 126 and 127 months.

Conclusions: In this comprehensive overview of the clinical features and outcomes of ANUMP, we conclude that ANUMP is a heterogenous disease with malignant behavior in the minority of patients. Correlating clinical findings with expert histopathologic review is crucial, and long-term follow up is important for the identification of metachronous metastatic disease.