A hypervascular perivascular epithelioid cell tumor of the urinary bladder showing TFE3 immunoreactivity clinically misdiagnosed as paraganglioma in an adolescent patient.

Perivascular epithelioid cell tumor (PEComa) of the urinary bladder is an exceptionally rare mesenchymal neoplasm and may be difficult to diagnose preoperatively. We report a rare case of a hypervascular bladder PEComa with TFE3 expression in an adolescent female that was clinically misdiagnosed as paraganglioma. A 16-year-old girl presented with intermittent gross hematuria. Imaging revealed a hypervascular submucosal bladder mass with marked homogeneous enhancement on computed tomography urography (CTU) and mild-to-moderate uptake on somatostatin receptor imaging, leading to suspicion of paraganglioma and preoperative α-adrenergic blockade. Histopathologic examination after transurethral resection showed epithelioid tumor cells with a low proliferative index. Immunohistochemistry demonstrated nuclear TFE3 positivity and strong cathepsin K expression, while melanocytic and neuroendocrine markers were negative, supporting a diagnosis of PEComa showing TFE3 immunoreactivity. The patient remains disease-free at six months of follow-up. This case highlights an important diagnostic pitfall of hypervascular bladder tumors mimicking paraganglioma, particularly in adolescent patients.