Case Report: The silent giant: biochemical-clinical dissociation in a large cystic pheochromocytoma

Background: Asymptomatic pheochromocytomas are increasingly detected as incidentalomas. However, large tumors presenting with marked biochemical elevation but complete clinical silence ("biochemical-clinical dissociation") are rare and prone to catastrophic mismanagement if mistaken for non-functional masses. Case presentation: We report a case of a 43-year-old normotensive female presenting with a large (57×53 mm) incidental left adrenal mass. Abdominal imaging revealed a cystic-solid tumor with intratumoral hemorrhage. Despite the complete absence of sympathetic symptoms, biochemical evaluation showed markedly elevated plasma normetanephrine levels (1168.0 pg/ml), indicating significant secretory activity. The patient was successfully managed with preoperative alpha-blockade (doxazosin) and volume expansion, followed by an uneventful transperitoneal laparoscopic adrenalectomy. Histopathology confirmed a pheochromocytoma with loss of SDHB expression. Conclusion: This suggests a multifactorial mechanism involving cystic sequestration and biochemical alterations associated with SDHB deficiency. Clinicians must recognize that biochemistry, not symptoms, dictates management. Mandatory preoperative α-blockade remains the cornerstone for preventing lethal intraoperative hemodynamic crises in these "silent" yet biochemically active tumors.