Atypical, Clinically Silent, Locally Advanced Pheochromocytoma Revealing Von Hippel-Lindau Type 2C Phenotype: A Case Report.

Pheochromocytomas are rare neuroendocrine tumors arising from chromaffin cells of the adrenal medulla. Malignancy is defined by the presence of distant metastases. Approximately a substantial proportion are associated with germline mutations, particularly in the context of Von Hippel-Lindau (VHL) syndrome. We report the case of a 60-year-old man diagnosed with a clinically silent locally advanced pheochromocytoma following a computed tomography-guided biopsy of a left retroperitoneal mass discovered during evaluation for persistent lower back pain. Biochemical evaluation revealed normal 24-hour urinary metanephrines despite markedly elevated chromogranin A levels. Imaging demonstrated an 80 × 76 mm left adrenal mass with locoregional invasion. Histopathological and immunohistochemical analyses confirmed pheochromocytoma. 123I-metaiodobenzylguanidine scintigraphy showed increased uptake in the adrenal region. Genetic testing identified a pathogenic VHL mutation: NM_000551.4(VHL):c.508G>A, consistent with VHL type 2C phenotype. Systematic screening for other VHL-associated lesions was negative. This case highlights the diagnostic challenge posed by clinically silent pheochromocytomas and underscores the importance of genetic evaluation in atypical adrenal tumors.