Abstract
RATIONALE: Undescended testis (cryptorchidism) is the most common congenital anomaly of the urogenital system. Testicular tissue exhibits variable fluorodeoxyglucose (FDG) uptake and may demonstrate a physiologically increased standardized uptake value. In cases of undescended testis with FDG uptake, immediate recognition can be challenging, increasing the risk of misinterpretation as a pathological lymph node. PATIENT CONCERNS: A 45-year-old male inpatient, was referred for ultrasound-guided biopsy of a right inguinal structure suspected to be a metastatic lymph node. Three weeks earlier, high-resolution computed tomography incidentally detected a cavitary pulmonary nodule, which was later confirmed as an adenocarcinoma through biopsy. For staging, an F-18 FDG positron emission tomography-computed tomography identified a solitary hypermetabolic inguinal lesion, raising suspicion of metastasis. DIAGNOSIS: Histopathological examination confirmed that the structure was an undescended testis, rather than a metastatic lymph node. INTERVENTIONS: The patient underwent an ultrasound-guided core needle biopsy under local anesthesia. OUTCOMES: The patient underwent a left upper lobectomy and had shown no signs of recurrence or bone metastasis to date. LESSONS: This case highlights the potential for misdiagnosis of an undescended testis as an inguinal metastatic lymph node due to physiological FDG uptake. Awareness of key imaging and clinical features, such as testicular mobility, relative isoechogenicity, and pain during biopsy, can help prevent unnecessary procedures and ensure an accurate diagnosis.