Renal hilar paraganglioma with atypical clinical presentation and biochemical functionality: A case report of diagnostic pitfalls.

Paragangliomas arising from the renal hilum are exceptionally rare and may mimic other retroperitoneal neoplasms on imaging. We report a 26-year-old normotensive man presenting with dull left flank pain. Biochemical evaluation showed elevated plasma free metanephrine and normetanephrine despite normal catecholamine levels. CT angiography demonstrated a thick-walled, multiseptated cystic hilar mass with renal vein encasement, while PET/CT showed low metabolic activity. Left nephrectomy with mass resection was performed, and histopathology with positive Synaptophysin, Chromogranin A, Vimentin, and S100 staining confirmed paraganglioma. This case highlights the diagnostic value of biochemical testing and histopathology in atypical renal hilar masses.