A rare presentation of metastatic thymic carcinoma mimicking pheochromocytoma and Von Hippel–Lindau syndrome: a case report

Abstract

Metastatic thymic carcinoma is a rare and aggressive malignancy that may present with atypical clinical and biochemical features, posing significant diagnostic challenges. We report the first documented case of metastatic thymic carcinoma mimicking both pheochromocytoma and Von Hippel–Lindau (VHL) syndrome. A 54-year-old man presented with neck pain, microscopic hematuria, bilateral adrenal masses, fluctuating hypertension, and borderline elevated plasma normetanephrine, raising suspicion for pheochromocytoma. Concurrent retinal abnormalities and cerebellar lesions suggested VHL syndrome. However, serial biochemical reassessment demonstrated normalization of catecholamine metabolites, while ophthalmologic evaluation reclassified the retinal findings as hypertensive retinopathy rather than retinal hemangioblastoma. Brain imaging showed features atypical for VHL-associated hemangioblastomas. ^68Ga-DOTATATE PET/CT demonstrated no significant tracer uptake in the adrenal or cerebellar lesions but revealed increased somatostatin receptor expression in an anterior mediastinal mass with tracer-avid lymph node and skeletal metastases. Histopathological examination of an adrenal mass confirmed metastatic basaloid squamous thymic carcinoma (CK5/6-positive, p63-positive, synaptophysin-negative, chromogranin-negative), excluding a neuroendocrine origin. This case highlights the remarkable ability of metastatic thymic carcinoma to mimic endocrine and hereditary syndromes, resulting in potential diagnostic pitfalls. A systematic diagnostic approach integrating serial biochemical testing, advanced functional imaging, comprehensive clinical reassessment, and histopathological confirmation is essential to establish the correct diagnosis. Metastatic thymic carcinoma should be considered in the differential diagnosis of adrenal masses with syndromic features, even when the initial presentation strongly suggests pheochromocytoma or VHL syndrome.