A potentially dangerous case of mistaken identity: giant asymptomatic composite phaeochromocytoma

Clinically silent PCC are increasingly common but are typically small, with relatively low levels of metanephrines. Upregulation of COMT causes intratumoural inactivation of catecholamines and may facilitate asymptomatic growth of PCC to a giant size. Measurement of metanephrine and normetanephrine levels in plasma or urine is the preferred biochemical investigation for PCC. Composite PCC are rare but have a similar clinical presentation and management to other PCC.