MON-522 - Composite Tumor of Myelolipoma with Mild Autonomous Cortisol Secreting Adrenocortical Adenoma

Introduction
Adrenal myelolipomas are benign tumors composed of adipose and myeloid tissue. They are discovered incidentally and are typically nonfunctional. We present a rare case of composite tumor of myelolipoma with mild autonomous cortisol secreting (MACS) adrenocortical adenoma (ACA).
Case Presentation
A 68 year old woman was referred for the evaluation of an incidental 3.5 cm left adrenal mass identified on CT abdomen 5 years prior to presentation. She had a history of atrial fibrillation, osteopenia, hypertension and chronic back pain. Physical examination did not reveal signs of Cushing’s syndrome. Endocrine evaluation showed ACTH 6.6 pg/mL (7.2-63.3), DHEA sulfate 62.9g/dL(65-370) and an abnormal overnight dexamethasone suppression test, with a post-test cortisol level of 4.3 mcg/dL indicating MACS. 24 hour urine cortisol, plasma metanephrines and aldosterone-renin ratio were normal. CT adrenal protocol demonstrated 36 HU heterogenous mass with a 40% absolute wash out and an interval increase in size to 4.7 cm in 5 years. Given atypical imaging characteristics, size and biochemical evidence of MACS, she underwent laparoscopic left adrenalectomy and was treated with hydrocortisone post-operatively. Histopathology showed 4 cm myelolipoma with a 1.5 cm yellow component composed of adrenocortical clear cells confirming composite tumor of myelolipoma and ACA.
Conclusion
Co-occurrence of ACA with MACS and myelolipoma is rare. Functional work up is crucial in all cases of myelolipoma as they can be associated with hormone excess due to concomitant ACA or hyperplasia. MACS is associated with osteoporosis and adverse cardiovascular outcomes; hence early identification and treatment can improve outcomes.

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