Choriogonadotropin positive seminoma-a clinicopathological and molecular genetic study of 15 cases

The presence of human chorionic gonadotropin (hCG) positive syncytiotrophoblastic cells (STC) in classic seminoma (CS) is well documented. CS with extensive hCG positive, non-syncytiotrophoblastic tumour cells (without STC) is exceptionally rare. In this study, we present 15 such cases. 168 CSs were retrieved from the Plzen Tumor registry. Cases of mixed germ cell tumors (with CS) and CSs with typical STC were excluded. Cases with completely embedded tumor mass were selected for further study and immunohistochemically examined with anti-hCG. Positive cases were further analyzed by reverse transcriptase polymerase chain reaction. Two groups of hCG-positive CSs were identified. Group 1 comprised 10 patients with a mean patient age of 37.7 years and mean tumor size of 4.96 cm. Eight cases were pT1 (TMN 2009) and 2 cases pT3a. Blood levels of hCG were elevated in 6 of the 10 patients preoperatively. In 2 patients the blood level of hCG was not tested. Mean follow-up period was 6.1 years. No metastatic behavior was noted. All tumors were extensively immunoreactive for hCG in more than 60% of tumor cells. The expression of hCG beta subunit (CGB)-mRNA in tumor tissue was documented. Group 2: Comprised 5 patients with a mean age was 34 years. Mean tumor size was 4.7 cm. Four cases were stage pT1 and 1 case was pT2. The mean follow-up period was 3.1 years. No metastatic behavior was noted. Preoperative blood levels of hCG were elevated in 1/5 of the patient. Strong hCG positivity was limited to scattered single tumor cells distributed throughout the entire tumor. Only weak expression of CGB mRNA was detected. We can conclude that immunohistochemical detection of expression of hCG in CS is not limited to syncytiotrophoblastic cells. In this study, we report two immunohistochemical patterns of hCG expression in classic seminomas: diffuse hCG staining in the majority of tumor cells and scattered hCG-positive cells within the tumor.