Utility of immunohistochemical investigation of SDHB and molecular genetic analysis of SDH genes in the differential diagnosis of mesenchymal tumors of GIT

Loss of expression of beta subunit of succinate dehydrogenase (SDHB) was proved to be present in a subgroup of KIT/PDGFRA wt gastrointestinal stromal tumors (GISTs). To evaluate possible diagnostic utility of SDHB immunohistochemistry in the differential diagnostics of mesenchymal tumors of gastrointestinal tract (GIT), 11 cases of KIT/PDGFRA wt GISTs, 12 gastric schwannomas (GSs), 20 solitary fibrous tumors (SFTs), 4 leiomyomas (LMs), 16 leiomyosarcomas (LMSs), 5 synovial sarcomas (SSs), 3 endometrioid stromal sarcomas (ESSs), and 1 ileal inflammatory myofibroblastic tumor (IMT) were investigated for SDHB immunoexpression together with molecular genetic analysis of genes encoding succinate dehydrogenase (SDH). Three recent cases of KIT/PDGFRA mutant GISTs were used as controls. Among the 11 KIT/PDGFRA wt GISTs, 6 expressed SDHB, 1 of them harboring a sequence change of SDHD. All SDHB-negative cases were SDHB-D wt. In 1 of the control GIST cases molecular genetic analysis revealed an SDHD sequence change in addition to a mutation in KIT exon 11. No SFT was truly SDHB-negative, but in 2 of them the staining was impossible to analyze. Furthermore, 1 SFT carried an SDHB and another 1 SDHD sequence change. All GSs, LMs, LMSs, SSs, ESSs, and IMT were SDHB-positive or non-analyzable, and SDHB-D wt. Additional factors may play a role in regulating expression of SDHB. Furthermore, SDHB immunohistochemistry alone may be misleading in excluding tumors other than GIST (especially SFT) in the differential diagnosis of KIT/PDGFRA wt mesenchymal tumors of GIT.

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.