SUN-482 - Adrenocortical Carcinoma Following GIST: A Case Highlighting Diagnostic and Genetic Considerations

Adrenocortical carcinoma (ACC) is a rare endocrine malignancy that can be difficult to diagnose, with an estimated 38% presenting as adrenal incidentalomas. Pathologic diagnosis is made from surgical adrenalectomy specimen, although image guided biopsy of adrenal tumors may be considered if extra-adrenal primary malignancy is suspected. Here we present an unusual case of ACC in a 67-year-old female, who presented with left adrenal nodule during surveillance for gastrointestinal stromal tumors (GIST).

The patient had four synchronous GIST tumors resected two years prior to the diagnosis of adrenal nodule. She had germline testing notable for NTHL heterozygous pathogenic variant, PTCH1 heterozygous variant of unknown significance. A 2.4-cm left adrenal adenoma was discovered on cross-sectional surveillance with computed tomography (CT). After exclusion of pheochromocytoma, she underwent CT guided biopsy reporting benign adrenal tissue without evidence of metastatic GIST. Subsequent biochemical workup revealed abnormal 1mg dexamethasone suppression test suggesting autonomous cortisol production. A laparoscopic left adrenalectomy was conducted, and pathology was reported as benign adrenal adenoma.

Fifteen months later, she presented with facial plethora, supraclavicular fullness, severe proximal muscle weakness, lower extremity edema, multiple ecchymoses and resistant hypertension. Laboratory evaluation showed severe hypokalemia despite potassium supplementation and spironolactone use. Cushing syndrome was diagnosed with elevated 24-hour urine free cortisol at 685 mcg/24 hours (4-50), evening cortisol was 67.9mcg/dL (2.7-10.5mcg/dL) while ACTH was undetectable. CT abdomen revealed recurrent disease in the left adrenal bed and metastatic disease to the liver. A liver biopsy confirmed ACC. Reevaluation of the original adrenalectomy specimen showed multiple histopathological features that suggest malignant behavior based on Weiss scoring criteria. Medical treatment for hypercortisolemia was initiated with metyrapone, and mitotane was added as part of neoadjuvant chemotherapy with Etoposide, Doxorubicin, Cisplatin, (EDP-M).

This case highlights pitfalls in diagnosis of ACC, particularly in the setting of a secondary malignancy. Pathologic misdiagnosis occurs in up to 9-13% of cases, even in expert centers. Although ACC and GIST are not known to be directly associated, both are linked to hereditary cancer syndromes, and patients with GIST have a 20.1% risk of second neoplasia.

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