Pseudopheochromocytoma: A Case of Benign Endothelial Cyst of the Adrenal Gland

Background: Benign endothelial cyst of the adrenal gland (ECAG) with pheochromocytoma-like symptoms, or pseudopheochromocytoma (pseudoPHEO), is an extremely rare condition. Adrenal cysts seldomly occur with an incidence of 0.06% in the general population. Most cases are asymptomatic and discovered incidentally on imaging. ECAG predominately affect females and represent approximately 45% of all cystic tumors involving adrenal glands with two subtypes: angiomatous and lymphangiomatous. The association of adrenal cysts with pseudopheochromocytoma is a rare but well-documented relationship. Occasionally, these cysts can increase pressure in the adrenal medulla leading to elevated metanephrine levels. PseudoPHEO is a diagnosis of exclusion with pheochromocytoma being an important differential diagnosis. Patients may present with pheochromocytoma-like features such as symptomatic paroxysmal hypertension. If adrenal cortical tumors are involved, elevated catecholamines can be found on evaluation, although catecholamine-secreting tumors are diagnosed in less than 0.5% of patients with hypertension. Case Information: A 63-year-old female with a past medical history of an adrenal nodule discovered in 2017 during colon resection and poorly-controlled hypertension presented for adrenalectomy for suspected pheochromocytoma. Her normetanephrine level was 342 (normal: <148pg/mL) and metanephrine was 50 (normal: <57pg/mL). CT of the abdomen demonstrated an adrenal lesion with some features of benign etiology. She underwent robotic-assisted laparoscopic right adrenalectomy during which a 3 cm cyst in the adrenal medulla was found abutting the adrenal cortex. Microscopically, a multilocular cyst associated with hemorrhage involving the adrenal medulla was present. Conclusion: To diagnose pseudoPHEO, pheochromocytoma must be excluded especially when symptomatic paroxysmal hypertension is present with or without elevated catecholamines. The cells were positive for CD31 and negative for calretinin on immunohistochemistry staining which support an endothelial cell origin consistent with benign ECAG, not pheochromocytoma. These cysts may occupy space in the adrenal gland, increasing pressure in the adrenal medulla to cause elevated metanephrines, as seen in this patient. While the prognosis for ECAG is good, ECAG with associated pseudopheochromocytoma can cause life threatening complications. Treatment of pseudoPHEO is dependent on severity and etiology of disease process. Medical management can be complicated by unpredictable episodes of hypotension as patients can be normotensive between symptomatic episodes. In cases of pseudopheochromocytoma caused by ECAG, adrenalectomy is often indicated.