[A Case of Metastatic Seminomatous Testicular Tumor with Complicated Diagnosis by FDG-PET].

18F-fluorodeoxy glucose positron emission tomography (FDG-PET) for evaluation of the post chemotherapy residual tumor of the seminomatous testicular germ cell tumor is recommended by several guidelines. We report a case whose residual tumor was evaluated by FDG PET but the results were difficult to interpret. A 41-year-old male with left seminomatous germ cell tumor of the testis and 60 mm retroperitoneal lymph node (RPLN) metastasis was referred to our hospital. The International Germ Cell Consensus Classification (IGCCC) was good prognosis. After high orchiectomy, three cycles of bleomycin, etoposide, and cisplatin (BEP) chemotherapy normalized the tumor marker and the RPLN decreased to 15 mm. The standardized uptake value (SUV) max at the RPLN by FDG-PET was 2.93. Although residual viable cells were suspected, the SUV max was relatively low. Thus surveillance without additional therapy was selected. After observation for 25 weeks, the tumor grew to 25 mm. Then four cycles of paclitaxel, ifosfamide, and cisplatin (TIP) chemotherapy were indicated for the recurrence. The RPLN was decreased to 15 mm, but the SUV max was still as high as 2.67 at 6 weeks after the last chemotherapy. We dissected the residual tumor suspecting viable cancer, but the pathological examination revealed necrotic tissue without any viable cells. He has had no signs of recurrence for 1 year and 9 months after the operation.