Radiological clues for diagnosing intra-abdominal seminoma in undescended testis on computed tomography

We report a case of intra-abdominal seminoma in an undescended testis, focusing on the radiological clues for diagnosis on computed tomography. A 49-year-old man visited our hospital with a palpable abdominal mass and underwent abdominopelvic computed tomography. Computed tomography demonstrated an ovoid, mildly enhanced, well-defined mass measuring 21 × 16 × 9 cm in the small bowel mesentery mimicking a mass of mesenteric origin. However, a vascular structure was observed in the left posterior aspect of the mass. The vascular structure originated from the inferior posterior part of the mass and ran cranially. The artery subsequently united to the aorta, and the vein united to the left renal vein. We identified the artery and vein as the testicular artery and vein, respectively. We also noted the absence of a left spermatic cord in the left inguinal canal. Therefore, we concluded that the mass originated from the left undescended testis. The patient underwent surgery, and the mass was removed with the testicular vessels; the resected testicular vein was mostly filled with thrombus. On pathological examination, the mass was confirmed to be a seminoma in the undescended testis.