Abstract Disclosure: M. Arumugam: None. G. Kim: None. Introduction: Adrenocortical carcinoma (ACC) is a rare endocrine malignancy that typically presents with characteristic clinical and biochemical manifestations that are aggressive in nature. We present a case of ACC which was incidentally noted on imaging with no symptoms or signs of hormone excess. Case report: A 62-year-old male was noted to have an adrenal mass during evaluation of 30 lb unintentional weight loss and failure to thrive. The adrenal mass measured 18.3 x 14.4 x 6.8 cm with central necrosis and demonstrated extrinsic mass effect on surrounding structures. He denied any symptoms of hypercortisolism or clinically apparent androgen excess. He quit smoking 31 years ago and occasionally chews tobacco. Overnight dexamethasone suppression test with 2 mg dexamethasone showed an appropriately suppressed cortisol of 1.3. Androgen levels including DHEA-S, androstenedione, testosterone, and 17 hydroxy-progesterone were all within the normal range. PET CT revealed intensely increased radiotracer uptake in a large central necrotic mass in left adrenal gland, suggestive of malignant neoplasm. No other abnormal radiotracer activity was noted to suggest metastasis. The patient underwent left adrenalectomy. Intraoperatively, invasion of left kidney and tail of the pancreas was noted. Left nephrectomy was performed, and the pancreas was dissected off. The pathologist used three different staging systems to characterize the adrenal tumor. The Helsinki scoring system and Reticulin Algorithm were consistent with Adrenocortical Carcinoma. The Lin-Weiss-Bisceglia grading interpreted it as adrenal oncocytic neoplasm of uncertain malignant potential. Given the latter interpretation, the case was sent to Massachusetts General Hospital (MGH) for expert opinion. MGH deemed the tumor to be low-grade adrenocortical carcinoma. Conclusion: This is an uncommon presentation of adrenocortical carcinoma with patient presenting with weight loss and failure to thrive but without biochemical findings such as elevated cortisol or androgens. Presentation: 6/1/2024