Extra-Adrenal Paraganglioma Mimicking a Hilar Lymph Node Metastasis From Testicular Cancer: A Case Study

Extra-adrenal paraganglioma is a rare tumor and is difficult to diagnose. We report a case of extra-adrenal paraganglioma in the hilum identified after treatment for multiple intrathoracic lymph node metastases from testicular cancer. A 32-year-old man presented to the hospital with a cough. Computed tomography revealed multiple lung tumors and intrathoracic lymph node swelling. The patient was diagnosed with left-sided testicular cancer with multiple intrathoracic metastases. A left orchiectomy was performed, followed by chemotherapy. A lung biopsy confirmed the absence of residual cancer. Three months after the lung biopsy, ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography revealed fluorodeoxyglucose uptake in the right hilum. Suspecting lymph node metastasis from testicular cancer, we performed tumor resection. Pathological findings diagnosed the lesion as a paraganglioma. Diagnosing extra-adrenal paraganglioma hidden by a primary tumor is highly challenging without complete remission of the primary tumor.