[Burned-out testicular germ cell tumors: a clinicopathological analysis of three cases].

To investigate the clinicopathological features and possible mechanisms of burned-out testicular germ cell tumors. The clinical and imaging data, histology and immunophenotypic characteristics of three cases of burned-out testicular germ cell tumors diagnosed at the Ruijin Hospital, Medical College of the Shanghai Jiaotong University, from 2016 to 2020 were retrospectively analyzed. The relevant literature was reviewed. The mean age of the three patients was 32 years. Case 1 had an elevated preoperative alpha-fetoprotein level (810.18 μg/L) and underwent "radical pancreaticoduodenectomy and retroperitoneal lesion resection" for a retroperitoneal mass. Postoperative pathology showed embryonal carcinoma, which needed to exclude gonadal metastasis. Color Doppler ultrasound showed a solid mass of the right testis, with hypoechoic lesion and scattered calcification in some areas. Case 2 was a "right supraclavicular lymph node biopsy specimen." Chest X-ray showed multiple metastases in both lungs. The biopsy showed metastatic embryonic carcinoma and bilateral testicular color Doppler ultrasound revealed abnormal calcifications in the right testicle. Case 3 showed a cystic mass of the right testis with calcification and solid areas. All 3 patients underwent radical right orchiectomy. Grossly, borders of the testicular scar areas were well defined. Cross sectioning of the tumors showed a gray-brown cut surface and single focus or multiple foci of the tumor. The tumor maximum diameter was 0.6-1.5 cm. Microscopically, lymphocytes, plasma cells infiltration, tubular hyalinization, clustered vascular hyperplasia and hemosiderin laden macrophages were found in the scar. Atrophic and sclerotic seminiferous tubules, proliferation of clustered Leydig cells and small or coarse granular calcifications in seminiferous tubules were present around the scar. Seminoma and germ cell neoplasia in situ were seen in case 1, germ cell neoplasia in situ was seen in case 2 and germ cells with atypical hyperplasia were seen in case 3. Immunohistochemistry showed that embryonic carcinoma expressed SALL4, CKpan(AE1/AE3) and CD30, seminoma and germ cell tumor in situ expressed OCT3/4, SALL4 and CD117, and spermatogenic cells with atypical hyperplasia expressed CD99 and SALL4. The Ki-67 positive index was about 20%, while OCT3/4 and CD117 were both negative. Burned-out testicular germ cell tumors are rare. The possibility of gonad testicular metastasis should be considered first for extragonadal germ cell tumor. If fibrous scar is found in testis, it must be determined whether it is a burned-out testicular germ cell tumor. The burned-out mechanisms may be related to the microenvironment of tumor immune-mediated and local ischemic injury.