5179 Uncommon Benign Mimics Of Suspicious Adrenal Nodules

Abstract Disclosure: L. Zhu: None. L. Loh: None. V. Gan: None. P. Kek: None. Introduction: Adrenal incidentaloma is often detected in imaging studies. In addition to biochemical testing, imaging plays a key role in guiding the management of such lesions. We describe two uncommon cases of benign lesions masquerading as suspicious adrenal nodules. Case 1. A 54-year-old man with hypertension, diabetes, dyslipidaemia, ischaemic heart disease and atrial fibrillation (on warfarin) underwent CT scan to exclude malignancy when he presented with thigh DVT, and was found to have a right 3.2cm adrenal nodule. Adrenal hormone profile was unremarkable. CT contrast characterization showed attenuation of 30, 35, and 32 HU on pre-contrast, venous and 10-minute delayed phase respectively. Given the minimal enhancement in high density areas, possible haemorrhage was considered and he was put on imaging surveillance. CT scans over the following 5 years showed stability of the lesion, resolution of high-density areas, and pre-contrast attenuation of -35HU, suggestive of myelolipoma. Further follow-up over the next 2 years then revealed tumour enlargement to 8.5cm, progressive predominance of dense areas (58 HU), and development of compressive symptoms. In view of mass effect, growing heterogeneity and possibility of a collision tumour, right adrenalectomy was performed. Histopathology revealed myelolipoma with extensive haemorrhage and no evidence of malignancy. Case 2. A 65-year-old woman had hypertension, ischaemic heart disease, dialysis-dependent end-stage renal disease secondary to glomerulonephritis, and oncological history of left renal cell carcinoma (RCC) and low-grade papillary urothelial carcinoma, both surgically resected 10 years ago. A new 1.6cm right adrenal nodule was seen on her surveillance CT scan for RCC. It was not present in a CT scan 7 years ago. The nodule displayed suspicious features such as nodular avid rim enhancement, persistent enhancement on delayed phase of contrast washout and central cystic change. Biochemical screening revealed plasma free metanephrine of 0.33 nmol/L (NR: <0.33) and plasma free normetanephrine of 0.99 nmol/L (NR: <0.71). Other adrenal hormone profiles were unremarkable. Cystic phaeochromocytoma was suspected and she underwent right adrenalectomy and nephrectomy following alpha blockade. Histopathology revealed a well-circumscribed nodule in the supra-renal adipose tissue, with vascular proliferation and features of anastomosing haemangioma. The right kidney was reported to have acquired cystic disease associated RCC. She was well post-operatively and remained on follow-up with the urologist for her RCC. Discussion: Haemorrhagic adrenal myelolipoma and supra-renal anatomosing haemangioma are benign lesions that may have CT characteristics similar to those of sinister lesions. Pre-operative diagnosis can be challenging. Surgical excision may be required to confirm diagnosis and exclude malignancy. Presentation: 6/3/2024