Adrenal Tumors in a Tertiary Referral Center: Clinical Insights from a Six-Year Retrospective Cohort

Background/Objectives: Detection of adrenal tumors is increasing, mainly due to the widespread use and improved availability of radiological imaging. Their occurrence increases with age, and recent studies have reported a substantial increase in detection rates over the past few decades. This study aimed to describe the clinical spectrum and management of adrenal tumors in a real-world tertiary referral setting. Methods: This retrospective observational study was conducted to characterize the clinical presentation, diagnostic evaluation, management, and pathological spectrum of adrenal tumors treated at the University Clinical Center of Vojvodina between January 2020 and December 2025. This study included 862 patients with adrenal tumors from the outpatient clinic, day hospital, and hospital ward of the Clinic for Endocrinology, Diabetes, and Metabolic Disorders, University Clinical Center of Vojvodina, from January 2020 to December 2025. Results: Mean age was 60.73 ± 11.51 (range 19–90) years. Peak prevalence was observed in the seventh decade of life. Accordingly, 86.5% of tumors were smaller than 4 cm, 50.3% of tumors were detected in the left adrenal gland, and 14.4% were bilateral. Non-functioning tumors accounted for 85.3% of cases, while tumors showing biochemical cortisol autonomy, aldosterone-secreting tumors, and catecholamine-secreting tumors accounted for 5.7%, 4.4%, and 4.6%, respectively. CT-based assessment of tumors showed that 88.6% were adenomas, while 3.2% were cases of pheochromocytoma, 2.6% metastasis, 2.1% carcinoma, and, in smaller percentages, cysts, myelolipoma, macro- and micronodular hyperplasia, and other types. Tumor histopathology (n = 121) showed adenoma, pheochromocytoma, and metastasis as the most common (45.5%, 24%, and 10.7%, respectively). Patients with malignant lesions were significantly older than those with benign lesions (p < 0.01) and pheochromocytoma (p < 0.01). In the subgroup with histopathological diagnosis (n = 121), histopathology was significantly associated with tumor size (χ2(4) = 19.80, p < 0.001), which may reflect selection for surgery or biopsy. The mean age of patients with benign tumors, pheochromocytoma, and malignant tumors was 52.34 ± 13.86, 51.07 ± 12.35, and 63.73 ± 12.38, respectively. In the tissue-diagnosed subgroup, right-sided localization was more frequent among malignant tumors (p = 0.035), although the small number of cases warrants cautious interpretation. Conclusions: In our cohort, most adrenal tumors were benign and non-functioning, while hormonally active and malignant lesions represented a smaller but clinically important proportion requiring specialized evaluation and management. These findings provide real-world insights into adrenal tumor care in a tertiary referral setting and support the need for standardized data collection and prospective multicenter studies.