Biochemically 'active' pheochromocytoma can be clinically 'silent'.

Summary: A 55-year-old woman presented with ill-defined right abdominal pain and, on evaluation, was diagnosed to have a large right adrenal mass (9.5×8.5×8.7 cm). Although normotensive, she had markedly increased plasma free normetanephrine (8,500 ng/L (normal range: 20.10-135.40)). Pre-operatively, she received alpha-adrenergic receptor blockade (prazosin) followed by beta-adrenergic receptor blockade before undergoing right laparoscopic adrenalectomy. She had an uneventful intra- and post-operative period. The microscopic section of the tumour showed a 'zellballen' pattern, with nests separated by thin fibrovascular septae, consistent with pheochromocytoma. With the increasing accessibility of imaging technologies, asymptomatic pheochromocytoma detections are increasing. The absence of hypertension or metabolic features can be found in 30% of the cases of pheochromocytoma. Small tumour size, dopamine secretion, extensive necrosis, absence of neuropeptide Y, and adrenoreceptor desensitisation are possible explanations for normotensive status. Our case underscores the importance of ruling out pheochromocytoma in all adrenal incidentalomas, even in normotensive status. Learning points: With the increasing availability of imaging techniques, pheochromocytomas are increasingly detected as incidentalomas. Pheochromocytomas can be normotensive even with significantly higher catecholamine levels and large size. Secondary diabetes mellitus can be seen in up to 50% of cases of pheochromocytomas and paraganglioma, which generally resolves after successful biochemical remission. Adequate α-blockade is preferable to prevent intra-operative haemodynamic instabilities in normotensive pheochromocytomas.