Mixed germ cell sex cord-stromal tumors of the testis and ovary. Morphological, immunohistochemical, and molecular genetic study of seven cases

We present the morphological, immunohistochemical, and molecular genetic features of three cases of testicular and four cases of ovarian mixed germ cell sex cord-stromal tumors (MGSCT). The germ cells in the testicular MGSCTs morphologically differed from those in classical seminomas by lacking the typical square off quality of the nuclei. In contrast to the nuclei in classical seminomas, their size in testicular MGSCTs was smaller and nucleoli were inconspicuous and the cytoplasm was Periodic Acid-Schiff(PAS) negative. Quite on the contrary, the variability in the size of the nuclei of the germ cells in the testicular MGSCTs was more similar to that seen in the germ cells of spermatocytic seminomas. Immunohisto-chemically, the germ cells of MGSCTs in one case reacted positively with antibody to AE1-AE3 by paranuclear dotlike or rodlike positivity. All three testicular MGSCTs had a negative reaction with the rest of antibodies, including placental alkaline phosphatase (PLAP), OCT4, and c-kit protein. Ovarian MGSCT in our series differed from the testicular lesions in both the germ cell component and the sex cord component. The germ cells in all four ovarian cases had cytomorphological and immuno-histochemical features identical to those in classical seminomas/dysgerminomas. They possessed the typical square off quality of the nuclei, which were much more blastic, with more mitoses compared with the testicular tumors in our series, and they were PLAP (4/4), OCT4 (4/4) and c-kit protein (3/4) positive immunohisto-chemically. The cytoplasm of the germ cells in ovarian neoplasms contained PAS positive glycogen. Germ cells in one ovarian MGSCTs showed amplification of l2p. All other germ cells were negative for amplification of 12p. All five successfully analyzed cases showed no mutation in all studied exons and exon-intron junctions in c-kit and PDFGRA genes

Cancer testis antigen expression in testicular germ cell tumorigenesis

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.Modern Pathology advance online publication, 15 November 2013; doi:10.1038/modpathol.2013.183