SUN-373 Small Adrenal Incidentaloma Stable in Size Becoming a Stage IV Adrenocortical Carcinoma 10 Years Later in a Young Patient Carrying a Germline APC Variant of Uncertain Significance (VUS)

Recent guidelines on adrenal incidentalomas suggested that patients with an indeterminate adrenal mass on imaging choosing not to undergo adrenalectomy to repeat imaging with either unenhanced computed tomography (CT) or Magnetic resonance imaging with chemical shift analysis in 6 to 12 months. If the adrenal mass is non-functioning and stable in size, patients may not require any additional monitoring.We report here a case of a young woman known for a small adrenal mass, stable in size for 4 years who was ultimately diagnosed with a Stage IV adrenal cortical carcinoma (ACC) 10 years later. Case report. In 2006, a 32-year-old French Canadian woman was referred in endocrinology for evaluation of a left 2.7 x 2.0 cm incidentally discovered adrenal mass. On presentation, her hormonal work up included a normal 1mg overnight dexamethasone suppression test (DST) and dehydroepiandrosterone sulfate (DHEA-S) within normal limits. On unenhanced computed tomography (CT), the radiodensity of the adrenal mass was 23 Hounsfield units (HU). The patient was followed with adrenal imaging and hormonal investigation yearly for 4 years and the adrenal mass demonstrated no growth in 4 years. Ten years after initial presentation, in 2016, after five years lost to follow up the patient presented with renal colic. Urological CT has unexpectedly revealed that the left adrenal mass had significantly progressed measuring 9 x 8.2 cm and 2 new hepatic lesions were identified. Biochemical work up demonstrated hypercortisolism and hyperandrogenemia: plasma cortisol after 1 mg overnight DST was 486 nmol/L and DHEA-S was 14.0 mmol/L (N 0.9-6.5). Twenty-four-hour urine steroid profiling was consistent with an ACC co-secreting cortisol, androgens and glucocorticoid precursors. The diagnosis of ACC with hepatic ACC metastases was confirmed by histology. Following genetic analysis, germline heterozygous variant of uncertain significance (VUS) was identified in the exon 16 of the APC gene NM_000038.5:c.2414G>A,(p.Arg805Gln) (rs200593940). The patient had no clinical manifestations of familial adenomatous polyposis. Immunohistochemical staining of the ACC were positive for IGF-2 and cytoplasmic/nuclear β-catenin, however, no somatic APC or beta-catenin mutations were found. This case illustrates that 1) small adrenal incidentaloma stable in size may progress to ACC 2) better genetic characterization of these patients may eventually give clues to this unusual evolution.