Retroperitoneal schwannoma mimicking metastatic seminoma: case report and literature review
A 29-year-old man presented with the right testis enlarged for 1 month without causing any discomfort. Physical examination revealed that the right testis measured up to 6 cm × 5 cm × 4 cm, which was much bigger than the left testis. This patient's medical history was not unusual. Notably, his brother was diagnosed with seminoma 10 years ago but was still alive and in good health. CT of the chest and abdomen revealed a single abdominal mass (29 mm × 31 mm) located below the renal hilum along the para-aorta. The serum concentration of α-fetoprotein, human chorionic gonado-tropin, and lactate dehydrogenase were normal. Right radical orchiectomy was performed. The section of the right testis contained a light white uncapsulated mass, measuring 5 cm × 4 cm. Microscope examination revealed seminoma limited to the testis and epididymis without vascular/lymphatic invasion, making the clinical stage NB. The patient refused radiotherapy but underwent 3 cycles of cisplatin, etoposide, and bleomycin (PEB). Post-chemotherapy CT revealed persistence of the retroperitoneal mass, with no change in tumor size or characteristics ().\nRetroperitoneal lymph node dissection was performed, and the harvested tissue contained negative lymph nodes but a single mass in the attached fat. The mass was diagnosed pathologically as retroperitoneal schwannoma and confirmed as such with immunohistochemistry (positive for S-100 and CD56, negative for CD34 and CD117). Cell proliferation was evaluated with Ki-67 staining, and a low proliferation rate (Ki-67 < 5%) was reported, supporting the benign nature of the lesion. Six months after the initial surgery, the patient was alive and in good health without any evidence of relapse. Complications such as retrograde ejaculation, ascites, and intestinal obstruction were not observed.