MON-508 A Neurofibroma Out of Place: Adrenal Gland as an Exceptionally Rare Location Presenting a Diagnostic Enigma

Abstract Disclosure: S. Dejprapasorn: None. P. Limumpornpetch: None. Introduction: Neurofibromas are benign peripheral nerve sheath tumors primarily associated with neurofibromatosis type 1 (NF1). While neurofibromas are commonly encountered as multiple lesions in NF1, solitary neurofibromas can arise independently of NF1 and are most frequently located on skin or peripheral nerves. Visceral neurofibromas are rare, and adrenal neurofibromas are exceptionally uncommon. This case highlights the diagnostic complexities posed by solitary adrenal neurofibroma, its implications for clinical management, and its significance in expanding the understanding of this rare entity. Clinical Cases: A 54-year-old male presented with progressive dyspnea and orthopnea over a year. A 4.8 cm mass of left adrenal gland was incidentally found during coronary CT imaging. Subsequent abdominal CT showed a 4.1x3.8 cm heterogeneous mass in left adrenal gland without distinguishing from pheochromocytoma, adrenocortical carcinoma (ACC), or metastasis. Hormonal evaluation ruled out cortisol hypersecretion, with a post-dexamethasone cortisol level of 0.58 μg/dL, and pheochromocytoma, with normal 24-hour urine fractionated metanephrines. Given mass size, and imaging characteristics with diagnostic uncertainty, laparoscopic adrenalectomy was performed. Gross examination revealed a well-defined, trabeculated grey-white mass measuring 5.5x5.0x3.5 cm. Histopathological analysis confirmed neurofibroma, characterized by spindle-shaped cells within a collagenous stroma, with immunohistochemistry positive for S-100 and CD34 and negative for SMA and desmin. Clinical Lessons: Adrenal neurofibromas, although exceedingly rare, should be considered in the differential diagnosis of adrenal masses with indeterminate imaging characteristics. Solitary neurofibromas, independent of NF1, have been documented in various visceral locations, including the kidney, colon, and bile duct. Adrenal involvement is particularly rare with only three cases reported in the literature to date. Adrenal neurofibromas typically present as well-defined hypodense features on CT. The heterogeneous enhancement in this case introduced significant diagnostic ambiguity, necessitating adrenalectomy. Histopathology remains the cornerstone for definitive diagnosis, with spindle-shaped cells and strong S-100 immunoreactivity serving as hallmark features. This case emphasizes the importance of a multidisciplinary approach to the effective management of rare adrenal masses. Conclusion: This case contributes to the limited literature and underscores diagnostic challenges. Surgical resection serves as both a therapeutic and diagnostic intervention. Comprehensive reporting of similar cases is crucial to enhance understanding and improve diagnostic accuracy, guiding optimal management strategies. Presentation: Monday, July 14, 2025