Endocrine Abstracts

JOINT2451

Introduction: Silent pheochromocytomas constitute a rare and heterogeneous clinical entity. These tumors are characterized by the absence of signs and symptoms of catecholamine excess and normal plasma and/or urinary metanephrines. We present three cases of silent pheochromocytomas.

Case 1: A 45-year-old female was referred for evaluation of a right adrenal incidentaloma detected on abdominal ultrasound. Subsequent imaging revealed a heterogeneous 2.9 cm mass with increased density (40 HU) on CT, and a slight loss of signal intensity in out-of-phase MRI images. Clinical and laboratory evaluations were normal; the patient was normotensive, and testing for cortisol, aldosterone, and urinary metanephrines was negative. The patient underwent uneventful laparoscopic adrenalectomy without preoperative α-adrenergic receptor blockade. Histology confirmed a pheochromocytoma with a potential biologically aggressive behavior (PASS = 4).

Case 2: A 68-year-old male with hypertension and diabetes was diagnosed during COVID-19 workup with a large right adrenal incidentaloma and a lesion with irregular borders in the left kidney. On CT, the adrenal mass measured 3.6 cm, had a high density (~30 HU), and showed no signal loss in out-of-phase MRI images. The 4.9 cm kidney lesion appeared heterogeneous. Clinical examination was unremarkable, while hormonal testing excluded hypersecretion of cortisol, aldosterone, or catecholamines. A PET-CT scan confirmed both lesions’ hypermetabolic nature. After multidisciplinary team discussion, the patient underwent resection of the kidney mass, followed by right adrenalectomy. No prior α-blockade was prescribed. Hemodynamic instability occurred during adrenalectomy. Histology revealed a clear-cell renal carcinoma and a pheochromocytoma with aggressive biological behavior (PASS = 9).

Case 3: A 64-year-old female with hypertension, prediabetes, and a history of surgical excision of a parathyroid adenoma was diagnosed with a 3 cm left adrenal incidentaloma upon work-up of an incident urinary track infection. Imaging suggested a non-benign lesion (high attenuation values and heterogeneity). Clinical examination was unremarkable except for paroxysmal hypertension over the previous four months. Hormonal evaluation (1 mg dexamethasone suppression test, plasma renin activity, serum aldosterone, and urinary metanephrines) was negative. ¹²³I-MIBG scintigraphy was suggestive of pheochromocytoma, and the patient was scheduled for left adrenalectomy with preoperative α-adrenergic receptor blockade. Histology confirmed the diagnosis of pheochromocytoma.

Conclusion: Despite negative biochemical testing, silent pheochromocytomas may retain some functionality. A personalized approach in terms of preoperative α-adrenergic blockade is warranted.