Molecular stability overrides size in giant pediatric pheochromocytoma.

OBJECTIVES: Pheochromocytoma is a rare but potentially life-threatening tumor in children, and its diagnosis may be challenging due to variable clinical presentations. We aimed to describe the diagnostic process and clinical outcomes of a child with a giant pheochromocytoma presenting with severe hypertension and metabolic abnormalities. CASE PRESENTATION: A 16-year-old female with a three-year history of hypertension and hyperglycemia, previously diagnosed with essential hypertension and type 2 diabetes mellitus, was found to have a 12.4 cm adrenal mass weighing 280 g. Congenital total hemihypertrophy provided an additional clinical clue. Biochemical evaluation demonstrated marked catecholamine excess, impaired glucose regulation (HbA1c: 6.4 %), low HOMA-IR (2.39), and markedly elevated plasma renin activity (60.8 ng/mL/h), consistent with secondary hyperaldosteronism. Following open total adrenalectomy, biochemical normalization and favorable radiological follow-up were achieved. Despite the large tumor size and multifocal lymphovascular invasion, preserved succinate dehydrogenase subunit B (SDNB) expression and a low Ki-67 proliferation index (2-3 %) were observed. CONCLUSIONS: This case highlights the importance of considering pheochromocytoma in children with persistent hypertension and atypical metabolic findings. Tumor size and individual histological features may not fully reflect biological behavior; integrated assessment incorporating molecular markers may improve risk stratification and clinical management.