CD10 is a cell surface neutral endopeptidase expressed by lymphoid precursor cells, germinal centre B lymphocytes, and some myelocytes.1 Therefore, it is used as marker for the categorisation of acute leukaemia and subclassification of lymphomas.2 With focus on germ cell tumours Del Sordo et al 3 reported in a cohort of 135 germ cell tumours expression of 92% for seminomas, whereas non-seminomatous germ cell tumours were negative. The authors concluded that CD10 serves to differentiate seminoma from non-seminomatous germ cell tumours. The aim of this study was to describe CD10 expression in the so far largest germ cell tumour set and to validate the findings of previous studies. ### Tissue microarray The tissue microarray used for this study has previously been described.4 It includes 325 testicular germ cell tumours: 207 classic seminomas, 4 spermatocytic seminomas, 19 pure embryonal carcinomas, 1 pure mature teratoma and 94 mixed germ cell tumours. In mixed germ cell tumours each component was separately punched and represented on the tissue microarray. Finally, 442 different histologic tumour components were considered for evaluation. ### Immunohistochemistry CD10 was detected using the prediluted antibody from Ventana (790–4506). The staining was performed with the Ventana Benchmark automated staining system (Ventana Medical Systems, Tucson, AZ). Samples were dichotomised into positive versus negative. The intensity of immunostaining was graded as absent, weak, moderate and strong. The threshold for …

Cancer testis antigens are encoded by germ line-associated genes that are present in normal germ cells of testis and ovary but not in differentiated tissues. Their expression in various human cancer types has been interpreted as ‘re-expression' or as intratumoral progenitor cell signature. Cancer testis antigen expression patterns have not yet been studied in germ cell tumorigenesis with specific emphasis on intratubular germ cell neoplasia unclassified as a precursor lesion for testicular germ cell tumors. Immunohistochemistry was used to study MAGEA3, MAGEA4, MAGEC1, GAGE1 and CTAG1B expression in 325 primary testicular germ cell tumors, including 94 mixed germ cell tumors. Seminomatous and non-seminomatous components were separately arranged and evaluated on tissue microarrays. Spermatogonia in the normal testis were positive, whereas intratubular germ cell neoplasia unclassified was negative for all five CT antigens. Cancer testis antigen expression was only found in 3% (CTAG1B), 10% (GAGE1, MAGEA4), 33% (MAGEA3) and 40% (MAGEC1) of classic seminoma but not in non-seminomatous testicular germ cell tumors. In contrast, all spermatocytic seminomas were positive for cancer testis antigens. These data are consistent with a different cell origin in spermatocytic seminoma compared with classic seminoma and support a progression model with loss of cancer testis antigens in early tumorigenesis of testicular germ cell tumors and later re-expression in a subset of seminomas.

Melanoma-associated gene C2 (MAGEC2) is a recently identified cancer testis antigen expressed in normal testicular and placental tissue. It has been detected in some human carcinomas, but its expression in primary testicular germ cell tumors is unknown. Immunohistochemistry was used to study MAGEC2 protein in 325 primary testicular germ cell tumors, including 94 mixed germ cell tumors. Seminomatous and non-seminomatous components were separately arranged and evaluated on tissue microarrays. MAGEC2 expression was compared with POU5F1 (OCT3/4), SOX2, SOX17, KIT and TNFRSF8 (CD30). The mouse monoclonal anti-MAGEC2 antibody (clone LX-CT10.5) revealed a nuclear MAGEC2 expression with little or no background staining. MAGEC2 expression was found in 238 of 254 seminomas (94%), but not in embryonal carcinomas (n=89). POU5F1 (OCT3/4) was positive in 97% of seminomas and all embryonal carcinomas. In contrast, KIT was positive in 94% of seminoma but also in 8% of embryonal carcinomas. TNFRSF8 (CD30) and SOX2 were negative in seminoma and positive in embryonal carcinoma (96 and 90%, respectively). SOX17 was positive in 94% of seminoma and negative in embryonal carcinoma. We conclude that MAGEC2 allows a reliable distinction of seminoma from embryonal carcinomas. Therefore, MAGEC2 represents an additional tool for the differential diagnosis of testicular germ cell tumors.

In this study we aimed to evaluate the protein expression of class I histone deacetylases (HDAC) in testicular germ cell tumours (GCT) and to analyse differences between the histological subtypes of testicular GCT. 325 testicular GCT were included in a tissue microarray with each histological subtype of the tumour being separately represented on this array. Expression of class I HDAC isoforms 1, 2 and 3 was assessed by immunohistochemistry. While HDAC2 and 3 were highly expressed in all histological subtypes of GCT, HDAC1 was almost consistently expressed at lower levels. We observed significant differences in the expression of the respective HDACs between seminoma and non-seminoma GCT tissue components. Interestingly, choriocarcinomas showed generally high expression values for all three class I HDAC isoforms. Relevant correlations with clinicopathological parameters could not be demonstrated. Contrasting published findings on other tumour entities, no immediate practical diagnostic or prognostic value for HDAC1-3 in GCT could be inferred. However, the high expression levels might still be indicative for a treatment response to HDAC inhibitors which ought to be evaluated in further studies.

Background It is difficult to predict the biologic behavior of pancreatic endocrine tumors in absence of metastases or invasion into adjacent organs. The World Health Organization (WHO) has proposed in 2004 size, angioinvasion, mitotic activity, and MIB1 proliferation index as prognostic criteria. Our aim was to test retrospectively the predictive value of these 2004 WHO criteria and of CK19, CD99, COX2, and p27 immunohistochemistry in a large series of patients with long-term follow-up. Design The histology of 216 pancreatic endocrine tumor specimens was reviewed and the tumors were reclassified according to the 2004 WHO classification. The prognostic value of the WHO classification and the histopathologic criteria necrosis and nodular fibrosis was tested in 113 patients. A tissue microarray was constructed for immunohistochemical staining. The staining results were scored quantitatively for MIB1 and semiquantitatively for CK19, COX2, p27, and CD99. The prognostic value of these markers was tested in 93 patients. Results The stratification of the patients into 4 risk groups according to the 2004 WHO classification was reliable with regard to both time span to relapse and tumor-specific death. In a multivariate analysis, the CK19 status was shown to be independent of the WHO criteria. By contrast, the prognostic significance of COX2, p27, and CD99 could not be confirmed. Conclusions The 2004 WHO classification with 4 risk groups is very reliable for predicting both disease-free survival and the time span until tumor-specific death. CK19 staining is a potential additional prognostic marker independent from the WHO criteria for pancreatic endocrine tumors.