Adrenal Pseudocyst Masquerading as Adrenocortical Carcinoma.

Incidental adrenal cysts are quite rare and thus can present a diagnostic conundrum for even experienced clinicians. Here, we present the case of a patient with an incidentally identified 5 cm adrenal mass. Her evaluation was notable for evidence of mild autonomous cortisol secretion and imaging findings concerning for malignancy with possible invasion of the inferior vena cava. Adrenalectomy was performed; pathology ultimately demonstrated an adrenal cortical pseudocyst without evidence of malignancy. All patients with solid, high-density, or large adrenal tumors require further imaging for characterization and biochemical testing for hormone secretion. While simple, low-density adrenal adenomas and cysts do not require further imaging evaluation beyond non-contrast CT, mixed cystic and solid lesions or pseudocystic lesions should be evaluated similarly to solid tumors, with the caveat that pseudocysts cannot always be well-differentiated from benign cysts on imaging. All adrenal incidentalomas should be evaluated with a biochemical work-up to assess hormonal activity. Tumors suspicious for malignancy require surgical excision. Patients with benign, hormonally active tumors should be managed surgically or medically, according to their primary pathology.