OCT4: a novel biomarker for dysgerminoma of the ovary

Application of stem cell markers in search for neoplastic germ cells in dysgenetic gonads, extragonadal tumours, and in semen of infertile men

Germ cell tumours (GCTs) are a complex entity. Current areas of attention include early detection and avoidance of unnecessary over-treatment. Novel findings regarding diagnosis of GCTs located in various anatomical sites are described, particularly testicular GCTs and their common progenitor, carcinoma in situ (CIS). Recognition of CIS enables intervention before tumour development, but nevertheless, testicular GCTs are sporadically diagnosed at the pre-invasive stage where minimal treatment is necessary. As presence of CIS is asymptomatic, a simple screening method is needed when CIS is suspected (i.e. in males investigated for infertility). To develop approaches for early detection CIS gene expression studies have been performed showing many similarities with embryonic stem cells with confirmation of established markers (i.e. PLAP, OCT-3/4, KIT) and identification of novel markers (i.e. AP-2 gamma, NANOG). We have reported a very promising new approach of AP-2 gamma (or OCT3/4) based immunocytological semen analysis (specificity 93.6%, sensitivity 54.5%). Comparative studies of gonadal/extragonadal GCTs have revealed resemblance pointing towards similar, but not identical, origins. Moreover, infertility and testicular cancer are connected in the 'Testicular Dysgenesis Syndrome' and 25% of contralateral testes from testicular GCT patients harbour dysgenetic features, including impaired spermatogenesis. Thus, recent data have provided potential diagnostic tools including CIS detection in semen, microarray-based tumour classification, additional serological GCT markers, and novel stem cell markers for immunohistochemical diagnosis of gonadal and extragonadal GCTs. Many CIS candidate genes are yet uninvestigated, and information from these could increase knowledge about CIS tumour initiation/progression and be used for optimisation of a non-invasive detection method.

The Differential Diagnosis of Central Nervous System Tumors: A Critical Examination of Some Recent Immunohistochemical Applications

Context.—As we write, novel antibodies that may well alter the routine practice of surgical neuropathology are in development, characterization, and the early stages of clinical use. These will be used for purposes of tumor subclassification, as prognostic markers, as identifiers of potential therapeutic targets, and as predictors of treatment response.

Objective.—To provide for nonspecialists a critical assessment of the peer-reviewed literature (necessarily colored by our own experience) as it pertains to several immunohistochemical reagents that have been recently forwarded as adjuncts to the histologic typing of central nervous system tumors.

Data Sources.—We address in these pages only antibodies that are commercially available, that have been the subjects of multiple published series, and that we have had occasion to use in the course of everyday problem solving.

Conclusions.—Discussion concentrates on the use of 4 antibodies: BAF47 in the diagnosis of atypical teratoid/ rhabdoid tumor, OCT4 in intracranial germinoma, β-catenin in craniopharyngioma, and NeuN as a marker of neuronal differentiation in neuroepithelial neoplasms.

Trials of new germ cell immunohistochemical stains in 93 extragonadal and metastatic germ cell tumors

Organic cation transporter 3/4 (OCT3/4) is a transcription factor of embryonic stem cells; c-kit (CD117) is a tyrosine kinase receptor implicated in seminoma carcinogenesis. Their reactivity is well characterized in testicular, but not extragonadal and metastatic, germ cell tumors. A total of 93 germ cell tumors (41 seminoma, 22 embryonal carcinoma, 18 teratoma, and 12 yolk sac tumor) were obtained from the central nervous system (30), mediastinum (23), retroperitoneum/abdomen (31), and other locations (9). Immunohistochemical staining for c-kit, placental-like alkaline phosphatase (PLAP), OCT3/4, and new markers D2-40 and AP-2gamma was performed on seminomas; CD30 and epithelial membrane antigen were added for nonseminomas. In embryonal carcinoma, c-kit reacted in 17 of 22 cases, OCT3/4 in 18 of 22, and PLAP in 13 of 22. OCT3/4 was superior to PLAP in intensity and percent cells staining. In seminoma, OCT3/4 and D2-40 were superior to PLAP in intensity and percent cells; c-kit and AP-2gamma were superior in percent cells. D2-40 stained 23 of 24 seminomas strongly but had only weak focal reactivity in 6 of 17 embryonal carcinomas. Sensitivity and specificity were high for OCT3/4 discriminating seminoma and embryonal carcinoma, and c-kit discriminating seminoma, from other germ cell tumors. For embryonal carcinoma, OCT3/4 had higher specificity (0.94) than CD30 (0.786) owing to CD30 reactivity in 3 of 10 teratomas. Epithelial membrane antigen discriminated teratoma from other nonseminomas with a sensitivity of 1 but reacted occasionally in embryonal carcinoma (3/15) and yolk sac tumor (2/7). In conclusion, for extragonadal seminoma, OCT3/4, AP-2gamma, D2-40, and c-kit were equivalently superior to PLAP. For embryonal carcinoma, OCT3/4 was superior to PLAP and more specific than CD30. D2-40 is recommended to discriminate between seminoma and embryonal carcinoma.

Aberrant expression and distribution of the OCT-4 transcription factor in seminomas

Testicular germ cell tumors (TGCTs), comprised of seminomas and non-seminomas, are derived from premalignant and noninvasive intracellular germ cell neoplasias. Among TGCTs, seminomas are believed to resemble a transformed state of primordial germ cells (PGCs) and are known to exhibit a gene expression profile similar to that of embryonic stem (ES) cells, such as transcription factor OCT-4. OCT-4 has recently been recognized as a diagnostic marker for clinical aspects of seminomas. However, the role of the OCT-4 protein in seminomas has not been clarified. To determine a possible role of the OCT-4 protein in seminomas, in this paper, we studied a series of 41 testicular tumor tissues and four cell lines by immunohistochemistry, Western blotting, and reverse-transcriptase polymerase chain reaction (RT-PCR) to examine the expression and distribution of the OCT-4 transcription factor in seminomas. By utilizing immunohistochemical staining and Western blotting, we demonstrated that the OCT-4 transcription factor was aberrantly localized in the cytoplasm and nuclei of cells in the collected seminoma tissues. This observation was further confirmed using immunocytochemical staining of NCCIT (seminoma-embryonal carcinoma) and NT2 (embryonal carcinoma) cells. In addition, the RT-PCR results indicated that Oct-4 mRNA was relatively highly expressed in NCCIT, NT2 cells, and seminoma tissues when compared with human embryonic stem cells. The aberrant expression and distribution of the OCT-4 transcription factor in seminomas may provide some important clues concerning the cell transformation between germ line stem cells (like PGC) and testicular germ cell tumors.

Recent Advances in the Pathology and Classification of Gonadal Neoplasms Composed of Germ Cells and Sex Cord Derivatives

In recent years, our understanding of neoplasms composed of germ cells and sex cord derivatives has increased. In this review, advances in the classification and pathology of ovarian germ cell-sex cord-stromal tumors are discussed. Only 2 neoplasms, each with a distinctive pathogenesis and clinicopathologic features, are included in this category. Gonadoblastoma is a tumor that usually occurs in the dysgenetic gonads of intersex patients that have a Y chromosome, whereas mixed germ cell-sex cord-stromal tumor arises in normal gonads in patients without sex chromosomal abnormalities. Ovarian mixed germ cell-sex cord-stromal tumors differ from their testicular counterparts in their histological appearance, immunohistochemical staining reactions, and biological behavior probably because the latter show a greater degree of maturity of their germ cell component. The introduction of cisplatin-based chemotherapy and the application of tumor markers have dramatically improved the clinical outlook for those patients who develop secondary malignant germ cell neoplasms.

Carcinomas of ovary and lung with clear cell features: can immunohistochemistry help in differential diagnosis?

Metastatic lung carcinomas with clear cell morphology can be confused with primary ovarian clear cell carcinomas. We performed immunohistochemical stains in 14 cases of non-small cell lung carcinomas with clear cell features and 14 cases of ovarian clear cell carcinomas using a panel of markers, including thyroid transcription factor 1 (TTF-1), carcinoembryonic antigen (CEA), Wilms tumor gene 1, octamer-binding transcription factor 4 (OCT-4), cancer antigen 125 (CA-125), estrogen receptor, and progesterone receptor. Among non-small cell lung carcinomas with clear cell features, 87.5% of adenocarcinomas (or 50% overall frequency in lung carcinomas) were positive for TTF-1, whereas none of the ovarian clear cell carcinomas were positive (P = 0.002). All 14 ovarian clear cell carcinomas stained for CA-125 as compared with 1 non-small cell lung carcinoma (P < 0.001). On the other hand, 85% of non-small cell lung carcinomas stained for CEA, whereas none of the ovarian clear cell carcinomas did (P < 0.001). Interestingly, 4 ovarian clear cell carcinomas (28%) showed positive staining for the germ cell marker OCT-4. Either lung or ovarian carcinomas stained for Wilms tumor gene 1, estrogen receptor, or progesterone receptor very infrequently; and the difference between the 2 groups was not statistically significant. Our results suggest that an immunohistochemical panel consisting of TTF-1, CEA, CA-125, and OCT-4 is helpful in distinguishing most pulmonary and ovarian carcinomas with clear cell features.

OCT4: biological functions and clinical applications as a marker of germ cell neoplasia

Germ cell tumours (GCTs) are a heterogeneous group of neoplasms, which develop in the gonads as well as in extragonadal sites, that share morphological patterns and an overall good prognosis, owing to their responsiveness to current surgical, chemotherapeutic, and radiotherapeutic measures. GCTs demonstrate extremely interesting biological features because of their close relationships with normal embryonal development as demonstrated by the pluripotentiality of some undifferentiated GCT variants. The similarities between GCTs and normal germ cell development have made it possible to identify possible pathogenetic pathways in neoplastic transformation and progression of GCTs. Genotypic and immunophenotypic profiles of these tumours are also useful in establishing and narrowing the differential diagnosis in cases of suspected GCTs. Recently, OCT4 (also known as OCT3 or POU5F1), a transcription factor that has been recognized as fundamental in the maintenance of pluripotency in embryonic stem cells and primordial germ cells, has been proposed as a useful marker for GCTs that exhibit features of pluripotentiality, specifically seminoma/dysgerminoma/germinoma and embryonal carcinoma. The development of commercially available OCT4-specific antibodies suitable for immunohistochemistry on paraffin-embedded specimens has generated increasing numbers of reports of OCT4 expression in a wide variety of gonadal and extragonadal GCTs. OCT4 immunostaining has been shown to be a sensitive and specific marker for seminomatous/(dys)germinomatous tumours and in embryonal carcinoma variants of non-seminomatous GCTs, whether in primary gonadal or extragonadal sites or in metastatic lesions. Therefore, OCT4 immunohistochemistry is an additional helpful marker both in the differential diagnosis of specific histological subtypes of GCTs and in establishing a germ cell origin for some metastatic tumours of uncertain primary. OCT4 expression has also been reported in pre-invasive conditions such as intratubular germ cell neoplasia, unclassified (IGCNU) and the germ cell component of gonadoblastoma. Additionally, OCT4 immunostaining shows promise as a useful tool in managing patients known to be at high risk for the development of invasive GCTs.

New immunohistochemical markers in the evaluation of central nervous system tumors: a review of 7 selected adult and pediatric brain tumors

CONTEXT

Immunohistochemistry (IHC) has become an important tool in the diagnosis of brain tumors.

OBJECTIVE

To review the latest advances in IHC in the diagnostic neuro-oncologic pathology.

DATA SOURCES

Original research and review articles and the authors' personal experiences.

DATA SYNTHESIS

We review the features of new, useful or potentially applicable marker antibodies as well as the new uses of already established antibodies in the area of diagnostic neuro-oncologic pathology, focusing on the use of IHC for differential diagnosis and prognosis. We discuss (1) placental alkaline phosphatase, c-Kit, and OCT4 for germinoma, (2) alpha-inhibin and D2-40 for capillary hemangioblastoma, (3) phosphohistone-H3 (PHH3), MIB-1/Ki-67, and claudin-1 for meningioma, (4) PHH3, MIB-1/Ki-67, and p53 for astrocytoma, (5) synaptophysin, microtubule-associated protein 2, neurofilament protein, and neuronal nuclei for medulloblastoma, (6) INI1 for atypical teratoid/rhabdoid tumor, and (7) epithelial membrane antigen for ependymoma. All the markers presented here are used mainly for supporting or confirming the diagnosis, with the exception of the proliferation markers (MIB-1/Ki-67 and PHH3), which are primarily used to support grading and are reportedly associated with prognosis in certain categories of brain tumors.

CONCLUSIONS

Although conventional hematoxylin-eosin staining is the mainstay for pathologic diagnosis, IHC has played a major role in differential diagnosis and in improving diagnostic accuracy not only in general surgical pathology but also in neuro-oncologic pathology. The judicious use of a panel of selected immunostains is unquestionably helpful in diagnostically challenging cases. In addition, IHC is also of great help in predicting the prognosis for certain brain tumors.

Ovarian dysgerminomas are characterised by frequent KIT mutations and abundant expression of pluripotency markers

BACKGROUND

Ovarian germ cell tumours (OGCTs) typically arise in young females and their pathogenesis remains poorly understood. We investigated the origin of malignant OGCTs and underlying molecular events in the development of the various histological subtypes of this neoplasia.

RESULTS

We examined in situ expression of stem cell-related (NANOG, OCT-3/4, KIT, AP-2gamma) and germ cell-specific proteins (MAGE-A4, NY-ESO-1, TSPY) using a tissue microarray consisting of 60 OGCT tissue samples and eight ovarian small cell carcinoma samples. Developmental pattern of expression of NANOG, TSPY, NY-ESO-1 and MAGE-A4 was determined in foetal ovaries (gestational weeks 13-40). The molecular genetic part of our study included search for the presence of Y-chromosome material by fluorescence in situ hybridisation (FISH), and mutational analysis of the KIT oncogene (exon 17, codon 816), which is often mutated in testicular GCTs, in a subset of tumour DNA samples. We detected a high expression of transcription factors related to the embryonic stem cell-like pluripotency and undifferentiated state in OGCTs, but not in small cell carcinomas, supporting the view that the latter do not arise from a germ cell progenitor. Bilateral OGCTs expressed more stem cell markers than unilateral cases. However, KIT was mutated in 5/13 unilateral dysgerminomas, whereas all bilateral dysgerminomas (n = 4) and all other histological types (n = 22) showed a wild type sequence. Furthermore, tissue from five phenotypic female patients harbouring combined dysgerminoma/gonadoblastoma expressed TSPY and contained Y-chromosome material as confirmed by FISH.

CONCLUSION

This study provides new data supporting two distinct but overlapping pathways in OGCT development; one involving spontaneous KIT mutation(s) leading to increased survival and proliferation of undifferentiated oogonia, the other related to presence of Y chromosome material and ensuing gonadal dysgenesis in phenotypic females.

GCP6 binds to intermediate filaments: a novel function of keratins in the organization of microtubules in epithelial cells

In simple epithelial cells, attachment of microtubule-organizing centers (MTOCs) to intermediate filaments (IFs) enables their localization to the apical domain. It is released by cyclin-dependent kinase (Cdk)1 phosphorylation. Here, we identified a component of the gamma-tubulin ring complex, gamma-tubulin complex protein (GCP)6, as a keratin partner in yeast two-hybrid assays. This was validated by binding in vitro of both purified full-length HIS-tagged GCP6 and a GCP6(1397-1819) fragment to keratins, and pull-down with native IFs. Keratin binding was blocked by Cdk1-mediated phosphorylation of GCP6. GCP6 was apical in normal enterocytes but diffuse in K8-null cells. GCP6 knockdown with short hairpin RNAs (shRNAs) in CACO-2 cells resulted in gamma-tubulin signal scattered throughout the cytoplasm, microtubules (MTs) in the perinuclear and basal regions, and microtubule-nucleating activity localized deep in the cytoplasm. Expression of a small fragment GCP6(1397-1513) that competes binding to keratins in vitro displaced gamma-tubulin from the cytoskeleton and resulted in depolarization of gamma-tubulin and changes in the distribution of microtubules and microtubule nucleation sites. Expression of a full-length S1397D mutant in the Cdk1 phosphorylation site delocalized centrosomes. We conclude that GCP6 participates in the attachment of MTOCs to IFs in epithelial cells and is among the factors that determine the peculiar architecture of microtubules in polarized epithelia.

Comparative Analysis of Germ Cell Transcription Factors in CNS Germinoma Reveals Diagnostic Utility of NANOG

The homeodomain transcription factor, NANOG, along with OCT3/4 (POU5F1) and SOX2, is part of the core set of transcription factors that maintain embryonic stem cell self-renewal and pluripotency. Expression of NANOG has been detected in fetal germ cells and in gonadal germ cell tumors. To assess the diagnostic utility of NANOG in central nervous system (CNS) germ cell tumors, we analyzed its expression by immunohistochemistry in a series of 12 CNS germinomas and compared its expression with other stem cell markers. Strong nuclear expression of NANOG was demonstrated in >90% of the tumor cells in all cases. In contrast, expression of OCT3/4 and placental alkaline phosphatase was inconsistent and SOX2 was expressed in only rare cells. NANOG was not detected in tumor types frequently considered in the differential diagnosis of CNS germinoma: pineoblastoma, primitive neuroectodermal tumors, medulloblastoma, lymphoma, pituitary adenoma, atypical teratoid/rhabdoid tumor, Langerhans cell histiocytosis, and gliomas. These findings demonstrate that NANOG is a sensitive and specific marker of CNS germinoma. Compared with other currently used markers, NANOG may have superior diagnostic characteristics and can facilitate identification of germinomas in minute surgical biopsies commonly obtained from these tumors. These findings also suggest a potential biologic role for NANOG in maintenance of CNS germinoma.

Screening for Intratubular Germ Cell Neoplasia of the Testis Using OCT4 Immunohistochemistry

Specific populations of patients are at high risk for the development of germ cell neoplasia. OCT4 has been shown to be a sensitive and specific marker for intratubular germ cell neoplasia of the testis. Whether or not OCT4 immunohistochemistry is a clinically useful screening tool in patients at risk for developing malignant germ cell tumors is not currently known. We undertook immunohistochemical staining for OCT4 in a large series of patients who underwent testicular biopsy or orchiectomy for reasons other than for management of a testicular mass suspicious for malignancy (infertility, cryptorchidism, atrophic testicle, etc.). OCT4 nuclear staining was identified in germ cells in 6 of 157 patients, all of whom had clinical risk factors for the development of testicular germ cell tumors. Two of the 6 patients were under 1.5 years of age, making the significance of OCT4 positivity less certain in these cases. The remaining patients with OCT4-positive germ cells consisted of 3 adults and 1 7-year-old child. Intratubular germ cell neoplasia was identified by light microscopy in only 1 of the 6 OCT4-positive cases. OCT4 immunostaining was negative in all patients who presented with infertility and who had no additional germ cell tumor risk factors. OCT4 immunohistochemistry may be useful in identifying early forms of preinvasive germ cell neoplasia in patients with risk factors for the development of malignant testicular germ cell tumors. The low incidence of OCT4 positivity in the adult infertility patients argues against the routine use of OCT4 immunostains in testicular biopsies for infertility unless additional risk factors are present.

Recent Advances in the Pathology and Classification of Ovarian Germ Cell Tumors

In recent years, our knowledge of ovarian germ cell tumors has increased, and their classification has evolved. The introduction of cisplatin-based chemotherapy and the discovery of tumor markers, including alpha-fetoprotein and human chorionic gonadotropin, have dramatically changed the clinical outlook for most of these patients. In this review, recent advances in the classification and pathology of ovarian germ cell tumors are discussed. Where appropriate, comparisons are made with testicular germ cell tumors. The last section of the article discusses the pathogenesis of germ cell tumors. This review will emphasize the articles written in the last 10 years and those that have significantly advanced our knowledge of germ cell tumors in past decades.

Expression of OCT4 in the Primary Germ Cell Tumors and Thymoma in the Mediastinum

Primary germ cell tumors (GCTs) and thymoma are both located in the anterior mediastinum. A previous study has postulated that octamer binding transcription factor (OCT4) is a nuclear transcription factor that is expressed in pluripotent embryonic germ cells. This study examined OCT4 expression in GCTs and thymoma originating from the mediastinum. A retrospective study included 46 consecutive patients with GCTs conducted between 1983 and 2005, and 22 consecutive thymoma in the mediastinum whose tumors had been surgically excised. The 46 primary GCTs in mediastinum included teratoma (n=27; 58.7%), seminoma (n=10; 21.7%), yolk sac tumor (n=6; 13%), embryonal carcinoma (n=1; 2.1%), and mixed GCTs (n=2; 4%; one consisted of teratoma and yolk sac tumor, and the other teratoma, yolk sac tumor, and seminoma); and 22 thymoma including World Health Organization type A (n=3, 13.6%), type AB (n=4, 18.2%), type B1 (n=6, 27.3%), type B2 (n=4, 13.6%), and type B3 (n=5, 22.7%). Each tumor was examined with hematoxylin and eosin staining, and with antibodies to OCT4. All 10 seminoma cases, 1 embryonal carcinoma case, and 1 mixed GCT case containing seminoma were immunopositive for OCT4. On the other hand, the 22 thymoma, 6 yolk sac tumor, 27 teratomas, and 1 case with mixed GCT without component of seminoma were immunonegative for OCT4. We conclude that immunostaining with antibodies to OCT4 is a useful diagnostic tool in the identification of seminomas and primary embryonal carcinomas in GCTs originating from the mediastinum.

Controversies in the management of germ cell tumours of the ovary

PURPOSE OF REVIEW

Ovarian germ cell tumours are rare, but curable at all stages of disease. This review gives an outline of the main controversies regarding the management of this disease.

RECENT FINDINGS

Pelvic malignancies are very rare during pregnancy, which should avoid the need for radical surgery or termination in these patients. Also during pregnancy, AFP-L2 looks to be a promising tumour marker in detecting relapse. Malignant transformation of mature teratomas may be predicted by preoperative squamous cell antigen and tumour size. OCT4 immunohistochemistry has been shown to be a very useful adjunct in the diagnosis of dysgerminomas. The traditional method for grading immature teratomas is challenged by a new classification. Patients receiving cisplatin-based chemotherapy are at a higher risk of developing cardiovascular risk factors. There is a hint that high-dose chemotherapy may play a role in relapsed patients.

SUMMARY

Rarity of the disease means many controversies are difficult to resolve, with much reliance on using data from testicular cancer studies. Many clinicians still advocate adjuvant chemotherapy for stage I nondysgerminomatous tumours of grade 2 and above despite good evidence that surveillance is a safe option, and increasing concerns about life-threatening long-term effects of treatment.

Immunohistochemical and functional biomarkers of value in female genital tract lesions

There has been a marked expansion in the literature pertaining to the use of immunohistochemical markers in female genital tract pathology, especially with regard to diagnosis. This review provides a survey of the antibodies commonly used in the diagnosis of gynecological lesions grouped as to function or type. Prognostic or predictive markers are also discussed where appropriate, although few of these are of value in everyday practice. It is stressed that when immunohistochemistry is used diagnostically, panels of markers provide better information than reliance on a single antibody.

Germ cell tumors in the intersex gonad: old paths, new directions, moving frontiers

The risk for the development of germ cell tumors is an important factor to deal with in the management of patients with disorders of sex development (DSD). However, this risk is often hard to predict. Recently, major progress has been made in identifying gene-products related to germ cell tumor development (testis-specific protein-Y encoded and octamer binding transcription factor 3/4) and in recognizing early changes of germ cells (maturation delay, preneoplastic lesions, and in situ neoplasia). The newly recognized "undifferentiated gonadal tissue" has been identified as a gonadal differentiation pattern bearing a high risk for the development of gonadoblastoma. It is expected that the combination of these findings will allow for estimation of the risk for tumor development in the individual patient (high risk/intermediate risk/low risk). This article reviews the recent literature regarding the prevalence of germ cell tumors in patients with DSD. Some major limitations regarding this topic, including a confusing terminology referring to the different forms of intersex disorders and unclear criteria for the diagnosis of malignant germ cells at an early age (maturation delay vs. early steps in malignant transformation) are discussed. Thereafter, an overview of the recent advances that have been made in our knowledge of germ cell tumor development and the correct diagnosis of early neoplastic lesions in this patient population is provided. A new classification system for patients with DSD is proposed as a tool to refine our insight in the prevalence of germ cell tumors in specific diagnostic groups.

An ovarian dysgerminoma in Down syndrome. Hypothesis about the association

An 11-year-old girl with Down syndrome (DS) was operated for a stage I right ovary dysgerminoma. She is in good health 33 years later. Some data in the literature suggest that ovarian cancers could be slightly overrepresented in DS. Despite the rarity of ovarian dysgerminoma, our case is the fifth reported in DS. This case is the second one associated with a family history suggesting the possibility of a familial predisposition to cancer. A hypothesis explaining the development of dysgerminoma in DS is proposed.

Retroperitoneal seminoma in limited biopsies: morphologic criteria and immunohistochemical findings in 30 cases

The incidence of retroperitoneal seminoma is much less than that of its gonadal counterpart. Accurate diagnosis of retroperitoneal seminoma is critical, because it carries an excellent prognosis due to its favorable response to radiation therapy and/or cisplatin-based chemotherapy. However, correctly diagnosing a retroperitoneal seminoma may be challenging, especially when the biopsy material is limited. The present study was conducted to evaluate histologic findings and immunohistochemical staining patterns in biopsy specimens of retroperitoneal seminoma and to compare their utility as diagnostic tools. Thirty biopsy specimens of retroperitoneal seminoma were assessed for histologic characteristics and immunohistochemical expression of OCT4, c-kit, placental-like alkaline phosphatase, and cytokeratin AE1/AE3. The clinical information, morphologic features, and staining intensities and the percentages of positively staining tumor cells were analyzed. The mean age of patients was 38 years. Lymphocytic infiltration and nucleolar prominence in tumor cells were found in all 30 cases (100%). The incidence of other histologic characteristics were as follows: fibrous septa/stroma in 80% (24 cases), clear tumor cell cytoplasm in 70% (21 cases), tumor necrosis in 60% (18 cases), cellular pleomorphism in 53% (16 cases), granulomatous inflammation in 50% (15 cases), distinct cell borders in 46% (14 cases), intercellular edema in 23% (7 cases), and syncytiotrophoblasts in 3% (1 case). The mean mitotic count was 3 (range 0 to 15) per 10 high-power fields. All 30 cases (100%) of retroperitoneal seminoma revealed moderate to strong nuclear OCT4 staining in more than 50% of tumor cells. Twenty-one cases (70%) showed membranous expression of c-kit by tumor cells, with moderate to strong staining intensity in most cases. Variable degrees of staining for placental-like alkaline phosphatase were identified in 23 cases (77%) with occasional background staining artifact. Six cases (20%) displayed a positive cytokeratin AE1/AE3 staining pattern with weak to moderate intensity. In conclusion, the most common histologic findings in limited biopsy specimens of retroperitoneal seminoma were lymphocytic infiltration and nucleolar prominence in tumor cell nuclei. OCT4 immunostaining, with its superior sensitivity and easy interpretation compared with other markers, is a powerful tool for confirming the diagnosis of retroperitoneal seminoma.

OCT4 is superior to CD30 in the diagnosis of metastatic embryonal carcinomas after chemotherapy

Correctly diagnosing a metastatic germ cell tumor after chemotherapy may be challenging because of the diverse morphological manifestations of postchemotherapy tumors. Both OCT4 and CD30 are sensitive markers for the identification of primary embryonal carcinomas; however, loss of expression of CD30 (65%) has been reported in metastatic embryonal carcinomas after chemotherapy. The present study was conducted to evaluate the expression patterns of OCT4 and CD30 in postchemotherapy metastatic embryonal carcinomas and to compare their utility as diagnostic tools. Twenty-five cases of metastatic embryonal carcinoma after chemotherapy were immunohistochemically analyzed for CD30, OCT4, and cytokeratin AE1/AE3 expression. The staining intensities and the percentages of positively staining tumor cells were recorded. Nineteen (76%) of 25 cases revealed diffuse, moderate to strong nuclear OCT4 staining in postchemotherapy embryonal carcinomas. Among these 19 OCT4-positive cases, 8 also revealed diffuse and moderate to strong membranous CD30 staining. Seven of these OCT4-positive cases retained focal and weak CD30 expression. The remaining 4 OCT4-positive cases demonstrated a complete loss of CD30 expression. The 19 OCT4-positive cases showed a positive but variable cytokeratin AE1/AE3 expression pattern. Six (24%) of 25 cases were negative for both CD30 and OCT4 but demonstrated diffuse and strong cytokeratin AE1/AE3 staining. OCT4 is a useful diagnostic marker to identify metastatic embryonal carcinomas after chemotherapy, with a better sensitivity than CD30.

Chromosome 12p abnormalities in dysgerminoma of the ovary: a FISH analysis

Dysgerminoma is the most common malignant ovarian germ cell tumor and shares histological and immunophenotypical features with its testicular counterpart, seminoma. Chromosome 12p abnormalities are genetic hallmarks of testicular seminomas. Little is known about these genetic changes in dysgerminoma. We performed dual color fluorescence in situ hybridization (FISH) analyses with a centromeric alpha-satellite probe for chromosome 12 and a subtelomeric probe for 12p on paraffin-embedded tissue sections from 21 dysgerminomas and two gonadoblastomas. Chromosome 12p abnormalities were detected in 81% of dysgerminomas. In all, 57% of cases had only isochromosome 12p and 5% had only 12p overrepresentation. In all, 19% had both isochrome 12p and 12p overrepresentation. Gonadoblastomas were negative for isochromosome 12p or 12p overrepresentation. Chromosome 12p abnormalities are common in dysgerminoma of the ovary. FISH analyses for chromosome 12p abnormalities may be a useful diagnostic adjunct for confirming the diagnosis of dysgerminoma and for distinguishing it from nongerm cell malignancies that enter into the differential diagnosis.

Immunohistochemistry as a diagnostic aid in the evaluation of ovarian tumors

Aspects of immunohistochemistry (IHC), which are useful in the diagnosis of ovarian tumors (mostly neoplasms but also a few tumor-like lesions), are discussed. The topic is first approached by considering the different growth patterns and cell types that may be encountered. Then a few other specific situations in which IHC may assist are reviewed. Selected findings largely, or only, of academic interest are also mentioned. One of the most common situations in which IHC may aid is in the evaluation of tumors with follicles or other patterns which bring a sex cord-stromal tumor into the differential. The distinction between a sex cord tumor and an endometrioid carcinoma with sex-cord-like patterns may be greatly aided by the triad of epithelial membrane antigen (EMA), inhibin, and calretinin, the latter two being typically positive and EMA negative in sex cord tumors, the converse being typical of endometrioid carcinoma. It should be emphasized that granulosa cell tumors may be inhibin negative and, albeit less specific, calretinin is more reliable in evaluating this particular issue. Lack of staining for inhibin and calretinin may also be supportive in leading to consideration of diverse other neoplasms that may form follicles, including metastatic tumors as varied as carcinoid and melanoma. The well-known staining of the latter neoplasm for S-100 protein and HMB-45 may be very helpful in evaluating melanomas with follicular or other unusual patterns, a challenging aspect of ovarian tumor interpretation. The most common monodermal teratoma, struma ovarii, usually has an overt follicular pattern and is easily recognized, but recognition of unusual appearances ranging from oxyphilic to clear cell to various patterns of malignant struma may be greatly aided by a thyroglobulin or TTF 1 stain. IHC for neuroendocrine markers may assist in the diagnosis of primary and metastatic carcinoid tumor. The broad differential diagnosis of glandular neoplasms with an endometrioid-pseudoendometrioid morphology, or mucinous cell type, has been the subject of much exploration in recent years, particularly the distinction between primary and metastatic neoplasms. The well-known CK7 positive, CK20 negative phenotype of primary endometrioid carcinoma, and the converse profile in most metastatic large intestinal adenocarcinomas with a pseudoendometrioid morphology, has been much publicized but albeit an appropriate supportive adjunct in many cases, exceptions from the typical staining pattern may be encountered. It is even less helpful in the case of primary versus metastatic mucinous neoplasia. Evaluation of the expression of mucin gene products has shown mixed, essentially unreliable, results. Experience with other new markers, such as CDX-2, villin, beta catenin, and P504S (racemase), is limited but is in aggregate promising with regard to providing some aid in this area. The rare differential of metastatic cervical adenocarcinoma versus primary ovarian mucinous or endometrioid carcinoma may be aided by strong p16 staining of the former. Staining for alpha-fetoprotein may aid in confirming the diagnosis of endometrioid-like (and hepatoid) variants of yolk sac tumor. Ependymoma of the ovary may also have an endometrioid-like glandular pattern, but positive stains for glial fibrillary acidic protein contrast with the negative results in others neoplasms with a similar pattern. Immunostains may be very helpful in the evaluation of oxyphilic tumors and tumor-like lesions and in some unusual forms of clear cell neoplasia, such as clear cell struma, both subjects being reviewed herein. Immunostains may highlight both the presence and extent of epithelial cells in a variety of circumstances, including microinvasive foci in cases of serous borderline tumors and mucinous carcinomas, and in determining the extent of carcinoma cells and reactive cells within mural nodules of mucinous neoplasms. As in tumor pathology in general, various markers may be crucial in the diagnosis of small round cell tumors of the ovary, and familiar markers of epithelial, lymphoid, leukemic, and melanocytic neoplasms may assist in the analysis of high grade tumors with a poorly differentiated carcinoma, lymphoma-granulocytic sarcoma, malignant melanoma differential. The evaluation of ovarian cystic lesions may be aided by thyroglobulin or TTF 1 (cystic struma), glial fibrillary acid protein (ependymal cysts), and inhibin-calretinin (follicle cysts and unilocular granulosa cell tumors). Stains for trophoblast markers may occasionally aid in the evaluation of germ cell tumors, although routine stains should usually suffice; they may be of academic interest in confirming trophoblastic differentiation in some high grade surface epithelial carcinomas.

HIF-2alpha regulates Oct-4: effects of hypoxia on stem cell function, embryonic development, and tumor growth

The division, differentiation, and function of stem cells and multipotent progenitors are influenced by complex signals in the microenvironment, including oxygen availability. Using a genetic "knock-in" strategy, we demonstrate that targeted replacement of the oxygen-regulated transcription factor HIF-1alpha with HIF-2alpha results in expanded expression of HIF-2alpha-specific target genes including Oct-4, a transcription factor essential for maintaining stem cell pluripotency. We show that HIF-2alpha, but not HIF-1alpha, binds to the Oct-4 promoter and induces Oct-4 expression and transcriptional activity, thereby contributing to impaired development in homozygous Hif-2alpha KI/KI embryos, defective hematopoietic stem cell differentiation in embryoid bodies, and large embryonic stem cell (ES)-derived tumors characterized by altered cellular differentiation. Furthermore, loss of HIF-2alpha severely reduces the number of embryonic primordial germ cells, which require Oct-4 expression for survival and/or maintenance. These results identify Oct-4 as a HIF-2alpha-specific target gene and indicate that HIF-2alpha can regulate stem cell function and/or differentiation through activation of Oct-4, which in turn contributes to HIF-2alpha's tumor promoting activity.

Early diagnosis and predictors of malignancy of adnexal masses

PURPOSE OF REVIEW

Ovarian cancer is an important cause of death among women with a malignant gynecological tumor. Cure rates for the disease at an early stage are around 80-90%, but survival is only 50% as the majority of women already show advanced disease upon diagnosis. The combination of gynecological examination, ultrasonography, and systemic tumor marker assay is considered to be a good strategy for the early diagnosis of ovarian neoplasia.

RECENT FINDINGS

Today, new technologies such as ultrasonography and tumor marker assay have increased the diagnosis rate for adnexal masses. These non-invasive methods, however, frequently do not distinguish benign conditions from malignant ones, which results in unnecessary surgery. Transvaginal ultrasonography is useful for diagnosing adnexal masses, but benign and malignant adnexal masses can present similar morphological characteristics. Combination with color Doppler ultrasonography and/or tumor markers may improve the accuracy of the method. Gene-expression array, proteomics and mathematical models form new approaches, but proper prospective studies are needed to validate them.

SUMMARY

The techniques of pelvic examination, ultrasonography, color Doppler ultrasonography, and tumor markers can be indicated for the diagnosis of ovarian cancer. The differentiation between benign and malignant ovarian tumor is, however, a clinical challenge. Until better diagnostic methods become available, patients and their physicians can use these techniques to decide on management.

Expression of CD117 (c-kit) receptor in dysgerminoma of the ovary: diagnostic and therapeutic implications

The proto-oncogene c-kit encodes a tyrosine kinase receptor, c-kit (CD117), which has been implicated in the development of a number of human malignancies. While the preferential expression of this protein has been well documented in testicular seminomas, there is little data concerning its expression in dysgerminomas of the ovary. We examined the expression of c-kit in 30 cases of ovarian dysgerminomas using immunohistohemical staining with a polyclonal anti-CD117 antibody. Staining was graded in a semiquantitative manner as follows: negative (no staining), 1+(1-10% staining), 2+(10-29% staining), 3+(30-50% staining), or 4+ (>50% staining). Of the 30 cases examined, 26 (87%) demonstrated immunoreactivity for CD117. In total, 10 (33%) demonstrated 4+ staining; 9 (30%) demonstrated 3+staining; 3 (10%) demonstrated 2+staining; 4 (13%) demonstrated 1+staining; and 4 (13%) demonstrated no staining. In conclusion, CD117 immunoreactivity was detected in 87% of ovarian dysgerminomas, a finding that correlates with previously reported frequencies of CD117 expression in seminomas (78-100%). Thus, antibodies to c-kit may be a useful diagnostic marker for ovarian dysgerminoma. Although the prognosis of patients with dysgerminoma is generally good, this receptor could potentially serve as a target for site-specific immunotherapy as an alternative and/or complement to conventional treatment options.

Ectopic expression of Oct-4 blocks progenitor-cell differentiation and causes dysplasia in epithelial tissues

The POU-domain transcription factor Oct-4 is normally expressed in pluripotent cells of the mammalian embryo. In addition, germ-cell tumors and a few somatic tumors show detectable expression of Oct-4. While Oct-4's role during preimplantation development is to maintain embryonic cells in a pluripotent state, little is known about its potential oncogenic properties. Here we investigate the effect of ectopic Oct-4 expression on somatic tissues of adult mice using a doxycycline-dependent expression system. Activation of Oct-4 results in dysplastic growths in epithelial tissues that are dependent on continuous Oct-4 expression. Dysplastic lesions show an expansion of progenitor cells and increased beta-catenin transcriptional activity. In the intestine, Oct-4 expression causes dysplasia by inhibiting cellular differentiation in a manner similar to that in embryonic cells. These data show that certain adult progenitors remain competent to interpret key embryonic signals and support the notion that progenitor cells are a driving force in tumorigenesis.

OCT4: A sensitive and specific biomarker for intratubular germ cell neoplasia of the testis

PURPOSE

OCT4 (POU5F1, OCT3) immunostaining highlights pluripotent cells (embryonal carcinoma and seminoma) in primary testicular germ cell tumors, but its relative usefulness in diagnosing intratubular germ cell neoplasia, unclassified (IGCNU) is not well established. The present study aimed to establish OCT4 as a sensitive and specific maker for IGCNU, a putative precursor for adult germ cell tumors.

EXPERIMENTAL DESIGN

We evaluated OCT4 immunostaining in 44 cases of IGCNU from patients who had testicular germ cell tumors. In addition, 27 of the 44 IGCNU sections were also examined with antibodies to placenta-like alkaline phosphatase, the most frequently used immunohistochemical marker for intratubular germ cell neoplasia. Sections from the testes of 10 patients who had undergone orchiectomy for hormonal treatment of prostate cancer and from autopsies of 10 patients without histories of germ cell tumors were also examined for OCT4 immunostaining. The immunoreactivity of the autopsy tissues was determined with vimentin staining, and all were reactive.

RESULTS

In all 44 of the cases, antibody to OCT4 marked the nuclei of nearly all of the dysplastic cells of intratubular germ cell neoplasia but not non-neoplastic testicular cells. The staining intensity was strong in every case, and there was little or no background staining. All 20 of the control specimens (10 orchiectomy specimens from prostate cancer patients and 10 testes from autopsies) were completely negative for OCT4. The 27 cases that were stained with antiplacenta-like alkaline phosphatase antibodies showed staining of variable intensity in the areas of intratubular germ cell neoplasia, and there was a high level of background staining artifact.

CONCLUSIONS

OCT4 is a sensitive and specific maker for intratubular germ cell neoplasia.

Transcription factors GATA-4 and GATA-6, and their potential downstream effectors in ovarian germ cell tumors

Ovarian germ cell tumors (GCTs) are histologically heterogeneous neoplasms originating from activated germ cells, the oocyte stem cells. These rare tumors often contain many different tissues mixed together, and malignant components are occasionally hidden within benign tissues thus complicating the diagnosis. The reasons for the variable differentiation of germ cells are still largely unknown. As transcription factors GATA-4 and GATA-6 as well as their downstream factors (e.g. HNF-4, BMP-2 and Ihh) are essential for normal yolk sac development, we studied their expression in 19 ovarian GCTs. Endodermal markers were expressed distinctively in different GCT types. The malignant endoderm in yolk sac tumors expressed all factors of endodermal development included in the study. Dysgerminomas, on the contrary, expressed only GATA-4 and, in a minority of cases, Ihh and BMP-2. The results suggest that GATA-4 and GATA-6 detected in the ovarian GCTs have retained their normal function. The fact that GATA-6 and HNF-4 are expressed exclusively in endodermal tissues indicates that these transcription factors play a role in the differentiation of germ cells towards the endodermal phenotype. Analysis of the nuclear transcription factors in tumor tissue could serve as a new informative diagnostic tool for ovarian GCTs.

Identification of germ cells at risk for neoplastic transformation in gonadoblastoma: an immunohistochemical study for OCT3/4 and TSPY

Carcinoma in situ (CIS) is the precursor of malignant testicular germ cell tumors (GCTs) of adolescents and young adults, being the neoplastic counterpart of primordial germ cells/gonocytes. Carcinoma in situ cells will develop into invasive seminoma/nonseminoma. Gonadoblastoma (GB) is the precursor of invasive GCTs in dysgenetic gonads, predominantly dysgerminoma (DG). In this process, part of the Y chromosome (GBY region) is involved, for which TSPY is a candidate gene. A detailed immunohistochemical survey was performed for the known diagnostic markers, germ cell/placental alkaline phosphatase (PLAP), c-KIT, and OCT3/4, as well as testis-specific protein on the Y chromosome (TSPY) on a series of GBs, and adjacent invasive DGs. All 5 patients were XY individuals (4 females and 1 male). In contrast to c-KIT, PLAP was positive in all cases. The immature germ cells of GBs were positive for OCT3/4, whereas the mature germ cells were negative for this marker, but positive for TSPY. In every GB, a minor population of germ cells positive for both markers could be identified, similar to most CIS cells and early invasive DG. On progression to an invasive tumor, TSPY can be lost, a process that is also detectable in invasive testicular GCTs compared to CIS. These results indicate that GB is a heterogeneous mix of germ cells, in which the OCT3/4-positive cells have the potential to undergo progression to an invasive tumor. These early invasive stages are initially also positive for TSPY (like CIS), supporting a positive selection mechanism. Therefore, OCT3/4 in combination with TSPY is valuable to identify malignant germ cells in dysgenetic gonads. This could allow better prediction of the risk of progression to a GCT. In addition, the data support the model that GB represents the earliest accessible developmental stage of malignant GCTs.

OCT4 immunohistochemistry is superior to placental alkaline phosphatase (PLAP) in the diagnosis of central nervous system germinoma

OCT4 is an 18-kDa POU-domain transcription factor encoded by the POU5F1 gene. Also known as OCT3, OTF3, and POU5F1, OCT4 is involved in the initiation, maintenance, and differentiation of pluripotent and germline cells during normal development. It is expressed in mouse and human embryonic stem and germ cells but absent from all differentiated somatic cell types in vitro and in vivo. OCT4 has been detected in primary testicular germ cell tumors with pluripotent potential: seminoma and embryonal carcinoma. We investigated: 1) whether a similar pattern of expression is present in primary intracranial germinomas; and 2) how OCT4 compares with placental alkaline phosphatase (PLAP) in terms of specificity and sensitivity as a potential diagnostic tool. We examined histologic sections from 25 cases of germinoma in which paraffin blocks with sufficient material were available. All cases were reviewed and sections from 32 different blocks were obtained and immunostained for OCT4 and PLAP. Additionally, 49 primary and metastatic brain tumors that may be potentially confused with germinoma, either clinically or histologically, were investigated for OCT4 expression. All but one germinoma were pure (ie, lacking other germ cell components). Intense and often diffuse nuclear staining was detected in 100% of germinomas. PLAP immunoreactivity was detected in 23 of 25 cases and was absent in the remaining 2 cases. The intensity of OCT4 immunostaining was significantly better than that of PLAP. None of the 49 control cases, which included glioblastoma multiforme, pineoblastoma, pituitary adenoma, malignant lymphoma, metastatic melanoma, capillary hemangioblastoma, meningioma, schwannoma, and a variety of metastatic carcinomas showed immunoreactivity for OCT4. Our study demonstrates that OCT4 is a highly specific and sensitive immunohistochemical marker for primary intracranial germinomas. OCT4 should be part of immunoperoxidase staining panels in which germinoma enters the differential diagnosis.

Testicular germ-cell tumours in a broader perspective

The germ-cell tumours are a fascinating group of neoplasms because of their unusual biology and the spectacular therapeutic results that have been obtained in these tumours. Traditionally, this group of neoplasms is presented in an organ-oriented approach. However, recent clinical and experimental data convincingly demonstrate that these neoplasms are one disease with separate entities that can manifest themselves in different anatomical sites. We propose five entities, in which the developmental potential is determined by the maturation stage and imprinting status of the originating germ cell. Recent progress begins to explain the apparent unpredictable development of germ-cell tumours and offers a basis for understanding their exquisite sensitivity to therapy.

Diagnostic value of OCT3/4 for pre-invasive and invasive testicular germ cell tumours

Human testicular germ cell tumours of adolescents and adults (TGCTs), the seminomatous and non-seminomatous germ cell tumours, show morphological and biological similarities to normal embryonic development, presumably determined by their supposed cell of origin, the primordial germ cell/gonocyte. Based on this knowledge, OCT3/4, also known as POU5F1, was recently defined as a diagnostic marker for these tumour types. In the adult testis, positive immunohistochemistry for OCT3/4 is an absolute indicator for the presence of the TGCT precursor carcinoma in situ/intratubular germ cell neoplasia undifferentiated (CIS/ITGCNU), seminoma, and/or embryonal carcinoma. Several studies have confirmed this observation, using the same polyclonal antibody. The present study demonstrates the usefulness of OCT3/4 immunohistochemistry in a diagnostic setting of a consecutively collected series of more than 200 testicular tumours and over 80 testicular biopsies. Moreover, it is shown that a monoclonal antibody directed against OCT3/4 is as informative as the polyclonal antibody, both in immunohistochemistry and in western blot analysis. The antibodies are robust and applicable with different methods of pretreatment and storage of tissue. This allows routine application of this diagnostic marker.