Solid Pattern Yolk Sac Tumor: A Morphologic and Immunohistochemical Study of 52 Cases

Pathogenesis and pathobiology of testicular germ cell tumours: a view from a developmental biological perspective with guidelines for pathological diagnostics

Testicular germ cell tumours (GCT) are divided into three different subtypes (types I-III) regarding to their developmental origin, histological differences and molecular features. Type I GCT develop from disturbed primordial germ cells and most commonly occur in children and young adolescents, which is why they are referred to as prepubertal GCT. Type II GCT develop from a non-invasive germ cell neoplasia in situ (GCNIS) and show an isochromosome 12p (i12p) or gain of 12p material as a common and characteristic molecular alteration. Type III GCT originate from distorted postpubertal germ cells (e.g. spermatogonia) in adult patients and have changes on chromosome 9 with amplification of the DMRT1 gene. Type I GCT encompass prepubertal-type teratomas and yolk-sac tumours (YST). Type II GCT include seminoma, embryonal carcinoma, choriocarcinoma, postpubertal-type teratoma and postpubertal-type YST. Types I and II GCT both show similar morphology, but are separated from each other by the detection of a GCNIS and an i12p in type II GCT. For type II GCT it is especially important to detect non-seminomatous elements, as these tumours have a worse biological behaviour and need a different treatment to seminomas. In contrast to types I and II GCT, type III tumours are equivalent to spermatocytic tumours and usually occur in elderly men, with few exceptions in young adults. The development of types I and II GCT seems to depend not upon driver mutations, but rather on changes in the epigenetic landscape. Furthermore, different pluripotency associated factors (e.g. OCT3/4, SOX2, SOX17) play a crucial role in GCT development and can be used as immunohistochemical markers allowing to distinguish the different subtypes from each other in morphologically challenging tissue specimens. Especially in metastatic sites, a morphological and immunohistochemical diagnostic algorithm is important to detect small subpopulations of each non-seminomatous GCT subtype, which are associated with a poorer prognosis and need a different treatment. Furthermore, primary extragonadal GCT of the retroperitoneum or mediastinum develop from misguided germ cells during embryonic development, and might be challenging to detect in small tissue biopsies due to their rarity at corresponding sites. This review article summarises the pathobiological and developmental aspects of the three different types of testicular GCT that can be helpful in the histopathological examination of tumour specimens by pathologists.

Dysgerminomas: germ cell tumors exhibit high expression of PD-L1 and associated with high TILs and good prognosis

Ovarian germ cell tumors (OVGCTs) account for 28% of all diagnosed ovarian cancers, and malignant germ cell tumors specifically account for approximately 13% of diagnosed ovarian cancers in Saudi Arabia. Although most germ cell tumor patients have a high survival rate, patients who experience tumor recurrence have a poor prognosis and present with more aggressive and chemoresistant tumors. The use of immunotherapeutic agents such as PD-L1/PD-1 inhibitors for OVGCTs remains very limited because few studies have described the immunological characteristics of these tumors. This study is the first to investigate PD-L1 expression in ovarian germ cell tumors and explore the role of PD-L1 expression in tumor microenvironment cells and genetic alterations. A total of 34 ovarian germ cell tumors were collected from pathology archives. The collected tumor tissues included ten dysgerminomas, five yolk sac tumors, five immature teratomas, and one mature teratoma, and the remaining samples were mixed germ cell tumors. The tumors were analyzed using immunohistochemical analysis to determine PD-L1 expression, immune cell infiltration and cancer stem cell populations and their correlation with clinical outcome. Furthermore, the genetic alterations in different subtypes of germ cell tumors were correlated with PD-L1 expression and clinical outcome. Datasets for testicular germ cells (TGCTs) were retrieved from The Cancer Genome Atlas (TCGA) and analyzed using cBioPortal (cbioportal.org) and Gene Expression Profiling Interactive Analysis (GEPIA). Compared with yolk sac tumors, dysgerminomas highly express PD-L1 and are associated with high levels of tumor infiltrating lymphocytes (TILs) and stem cell markers. In addition, compared with PD-L1-negative yolk sac tissue, dysgerminomas/seminomas with high PD-L1 expression are associated with more genetic alterations and a better prognosis. Our findings will contribute to the knowledge about the potential benefits of ovarian cancer immunotherapy in specific subsets of germ cell tumor patients and the risk factors for resistance mediated by tumor microenvironment cells.

Primitive Embryonic-Type Neuroectodermal/Glandular Complexes in Testicular Germ Cell Tumors: A Mimic of Embryonic-Type Neuroectodermal Tumor

Embryonic-type neuroectodermal elements are often intimately mixed with primitive endodermal-type glands, like those of yolk sac tumors, in germ cell neoplasia in situ (GCNIS)-derived germ cell tumors of the testis. Because the primitive glands mimic tubules or rosettes of embryonic-type neuroectodermal elements, these embryonic-type neuroectodermal/glandular complexes may be misinterpreted as pure lesions of embryonic-type neuroectodermal elements, which, if of sufficient size, may lead to a diagnosis of embryonic-type neuroectodermal tumor, despite that the criteria of the World Health Organization for a "somatic-type malignancy" are not met. A diagnosis of embryonic-type neuroectodermal tumor in the testis may lead to retroperitoneal lymphadenectomy even in clinical stage I patients, and in postchemotherapy resections indicates a poor prognosis. The distinction of the neuroectodermal and glandular elements is not always straightforward based on morphology alone. We, therefore, studied 34 testis-derived germ cell tumors with embryonic-type neuroectodermal/glandular complexes and 2 purely glandular yolk sac tumors to characterize the immunophenotypes and determine an efficient immunohistochemical panel to aid in this differential. We found that GFAP, synaptophysin, and paired-like homeobox 2B (PHOX2B) expression was specific to embryonic-type neuroectodermal elements, although PHOX2B had poor sensitivity. In contrast, positive reactions with antibodies directed against AFP, villin, and CDX2 were specific for the glandular elements, although CDX2 had poor sensitivity. Other markers, including AE1/AE3 cytokeratin, SALL4, glypican 3, SOX2, SOX11, CD56, INSM1, and neurofilament, proved less helpful because of their nonspecificity and/or poor sensitivity. We conclude that the optimal immunohistochemical panel for distinguishing the components of embryonic-type neuroectodermal/glandular complexes includes stains for synaptophysin, GFAP, villin, and AFP.

Beta-Catenin Alterations in Postchemotherapy Yolk Sac Tumor, Postpubertal-Type With Enteroblastic Features

Postchemotherapy postpubertal-type yolk sac tumors (YST) with glandular and solid phenotypes are aggressive and commonly resistant to systemic chemotherapy. These neoplasms show morphologic features that significantly overlap with those of somatic carcinomas with "enteroblastic" or "fetal" phenotype (the preferred terminology depends on the site of origin). They often present as late or very late recurrences, and their diagnosis is challenging because they frequently affect patients in an age group at risk for carcinomas of somatic origin. Recently, we incidentally identified examples of postchemotherapy glandular and solid YST with "enteroblastic" phenotypes and nuclear expression of beta-catenin, prompting us to further evaluate the prevalence of this phenomenon. We found nuclear expression of beta-catenin in 10 (29%) of 34 such tumors. A subset of cases with nuclear beta-catenin expression was further analyzed with a DNA sequencing panel (n = 6) and fluorescence in situ hybridization for isochromosome 12p [i(12p); n = 5]. Sequencing identified exon 3 CTNNB1 variants in 3 (50%) of 6 analyzed cases, and fluorescence in situ hybridization was positive for i(12p) in 5 of 5 cases. In conclusion, a significant subset of postchemotherapy YST with glandular or solid architecture and "enteroblastic" phenotype demonstrates beta-catenin alterations, suggesting that activation of Wnt signaling may play a role in the progression of these neoplasms. Moreover, nuclear beta-catenin expression in these tumors represents a potential diagnostic pitfall given that carcinomas of true somatic origin with overlapping morphology may also be positive for this marker.

Primary germ cell tumours of the mediastinum: A review with emphasis on diagnostic challenges

This article will review current aspects of the histopathological, immunohistochemical and molecular analysis of primary mediastinal germ cell tumours (PMGCTs) as well as their aetiological, epidemiological, clinical and therapeutic features. PMGCTs represent an important differential diagnosis in the spectrum of mediastinal tumours, and their diagnosis is usually made on small tissue samples from core needle biopsies in combination with diagnostic imaging and serum tumour markers. As in lymphomas, a small biopsy is often the only viable tumour sample available from these patients, as they receive chemotherapy prior to eventual surgical resection. Pathologists therefore need to apply an efficient combination of immunohistochemical markers to confirm the diagnosis of a PMGCT and to exclude morphological mimics.

FoxA2 is a reliable marker for the diagnosis of yolk sac tumour postpubertal-type

AIMS

Yolk sac tumour postpubertal-type (YSTpt) shows a wide range of histological patterns and is challenging to diagnose. Recently, forkhead box transcription factor A2 (FoxA2) emerged as a driver of YSTpt formation and a promising marker for diagnosing YSTpt. However, FoxA2 has not been tested in the different patterns of YSTpt. This study aimed to assess the staining pattern of FoxA2 in te different patterns of YSTpt and other germ cell tumours of the testis (GCTT), comparing it with glypican-3 (GPC3) and α-fetoprotein (AFP).

METHODS AND RESULTS

FOXA2, GPC3 and AFP immunohistochemistry was performed on 24 YSTpt (24 microcystic/reticular, 10 myxoid, two macrocystic, five glandular/alveolar, two endodermal sinus/perivascular, four solid, two polyembryoma/embryoid body and two polyvesicular vitelline) and 81 other GCTT. The percentage of positive cells (0, 1+, 2+, 3+) and the intensity (0, 1, 2, 3) were evaluated regardless of and within each YSTpt pattern. FoxA2 was positive in all YSTpt (24 of 24) and all but one (23 of 24) exhibited 2+/3+ stain, with higher intensity [median value (mv): 2.6] than AFP (1.8) and GPC3 (2.5). Both FoxA2 and GPC3 were positive in all microcystic/reticular (24 of 24), myxoid (10 of 10), macrocystic (two of two), endodermal sinus/perivascular (four of four) and polyembryoma/embryoid body (two of two) patterns. Nevertheless, only FoxA2 was positive in all glandular/alveolar (five of five), solid (four of four) and polyvesicular vitelline (two of two) patterns. The intensity of FoxA2 was higher than AFP and GPC3 in almost all YST patterns. In the other GCTT, FoxA2 was positive only in teratoma postpubertal-type (Tpt) [13 of 20 (65%)], with staining almost exclusively confined to the mature gastrointestinal/respiratory tract epithelium.

CONCLUSIONS

FoxA2 is a highly sensitive and specific biomarker that supports the diagnosis of YSTpt. FoxA2 is superior to GPC3 and AFP, especially in rare and difficult-to-diagnose histological patterns of YSTpt, but mature glands of Tpt could represent a potential diagnostic pitfall.

Ovarian Malignant Mixed Germ Cell Tumor With Prominent Embryoid Bodies (Polyembryoma Background): A Case Report and Literature Review

Ovarian malignant mixed germ cell tumors are rare tumors occurring in young women. The presence of prominent embryoid bodies in these tumors is extremely uncommon. Herein, we report such a case, with a histomorphologic description and immunohistochemical and fluorescence in situ hybridization analyses.

Pure post-pubertal yolk sac tumor of the testis: An extremely rare and aggressive entity

CONTEXT

Pure post-pubertal yolk sac tumors (YSTs) are an extremely rare type of malignant germ cell tumor (GCT) that account for <1 % of testicular GCTs. Clinically, they are more aggressive compared to the more common pre-pubertal counterpart. The aim of this study is to analyze the clinical presentation, ancillary tests and clinical outcomes in addition to presenting a spectrum of histomorphological features, in a case series along with a literature review.

DESIGN

A retrospective review of 4 cases of pure post-pubertal YST of the testis was performed. Data collected for each patient included demographics, clinical presentation, serum markers, radiology and pathologic findings, treatment, and clinical outcomes.

RESULTS

All patients presented with a testicular mass with or without associated pain and elevated serum alpha-feto protein. Mean age at presentation was 36 years (range 25-68 years). Two patients presented with metastatic disease at the time of diagnosis. Histologic patterns and features are as follows: germ cell neoplasia in-situ (n = 4), reticular/microcystic, solid, glandular, papillary, endometrioid, cystic, necrosis and angiolymphatic invasion (n = 3). Fluorescent in-situ hybridization test performed on Case 2, showed presence of isochromosome 12p and next generation sequencing showed gains of 12p. Case 1, 2 and 4 showed metastatic disease on follow-up.

CONCLUSIONS

Diagnosis of pure post-pubertal YST remains challenging due to the variety of morphologic patterns often present in these tumors. Extensive sampling along with use of ancillary tests is the key for diagnosis. In this study, 75 % of cases had metastatic disease at or after the diagnosis confirming the aggressive nature of this rare entity.

An update on diagnostic tissue-based biomarkers in testicular tumors

Testicular cancer is rare overall but comprises the most common solid malignancy diagnosed in young men aged ∼20-40 years. Most testicular neoplasms generally fall into 2 broad categories: germ cell tumors (GCTs; ∼95%) and sex cord-stromal tumors (SCSTs ∼5%). Given the relative rarity of these tumors, diagnostic biomarkers are highly relevant for their diagnosis. Over the past several decades, diagnostic biomarkers have improved dramatically through targeted immunohistochemical and molecular characterization. Despite these recent advances, most markers are not perfectly sensitive or entirely specific. Therefore, they need to be used in combination and interpreted in context. In this review, we summarize tissue-based biomarkers relevant to the pathologist, with a focus on practical diagnostic issues that relate to testicular GCT and SCST.

Testicular Tumors: New Developments in Germ Cell and Sex Cord Stromal Tumors

This article reviews the recent advances and potential future changes in the classification of testicular germ cell and sex cord stromal tumors, highlighting changes in the classification system and terminology with description on newer entities. A discussion on approaching difficult areas and diagnostic pitfalls is also included along with the utility of ancillary investigations. Areas with limited knowledge are highlighted to providing direction for future studies and a bulleted summary in the form of critical care points is provided.

Yolk sac tumours of the orbit and sinonasal tract

PURPOSE

The aim of this study is to report two cases of paediatric Yolk sac tumours (YST) of the orbit and sinonasal tract, with a major review on the subject.

METHODS

Two case reports along with a comprehensive retrospective literature review of all English language publications between 1974 and 2021 is presented. Literature review examined the demographics, clinical presentation and diagnostic and prognostic factors of extragonadal YSTs of the orbit and sinonasal tract.

RESULTS

Orbit and sinuses are rare sites for YST, with only 25 paediatric cases reported in the literature. Extragonadal yolk sac tumours carry a significantly worse outcome than those localised to the gonads, with the 5-year survival of 66% and 81-89%, respectively. Our review found the median age of presentation to be 18 months (18 months for males and 24 months for females), and females are more commonly affected. The most common presentations were proptosis, facial swelling and ophthalmoplegia. Treatments and therefore outcomes varied in the cases due to the large time period. Of the cases reported in the last 10 years, all patients with data provided were alive and disease-free at follow-up.

CONCLUSION

Sino-orbital yolk sac tumours are rare and have variable presentations, dependent on the extent of local invasion. Early diagnosis and treatment with multimodal therapy are paramount in having improved overall survival.

Decoding germ cell tumours for clinicians

PURPOSE OF REVIEW

Germ-cell tumours of the testis affect predominantly younger males aged between 15 and 40 years, with nearly 74,500 new cases estimated globally in 2020. Their rarity and the complex morphology, mean that, in nonexpert hands, there is a significant risk of misdiagnosis of both type and staging of these neoplasms.

RECENT FINDINGS

There have been significant changes in the 2016 WHO classification of Testicular tumours that need to be understood by both pathologists and clinicians for streamlining management. Standardised structured reporting guidelines and discussion at the multidisciplinary-team meetings lead to subsequently better health outcomes and patient safety.

SUMMARY

Therefore, communication with high-quality reports and understanding of clinicians of what constitutes an adequate report, is the key to ensure proper management of these patients. We attempt to discuss the key updates and pathological features that influence management and need to be communicated with clarity and precision.

Yolk Sac Tumor of the Ovary: A Report of 150 Cases and Review of the Literature

One hundred fifty yolk sac tumors (YSTs) of the ovary in patients from 1 to 61 (mean: 21.5) years of age are described; 75% of the patients were in the second and third decades and only 1 was above 50 years of age. The clinical manifestations were typically related to a fast-growing adnexal mass; endocrine manifestations (hirsutism) were present in only 2 cases. The tumors were all unilateral and 70% were ≥15 cm; an associated dermoid cyst was present in 20 cases. The tumors were solid and cystic in 57% of the cases, 25% were multicystic, and 18% uniformly solid. The solid tissue was typically tan to pink or yellow and often friable with hemorrhage and necrosis; smaller solid neoplasms were sometime uniformly yellow. The most common histologic pattern was reticular composed of an irregular meshwork of spaces that was conspicuous in 68% of the neoplasms but present to at least a minor degree in all of them. That appearance almost always merged with small to large cysts that were prominent in about 40% of tumors. In 25% of the tumors, cysts sometimes associated with a cellular stroma (the polyvesicular pattern), were present but conspicuous in only half these cases. One third of the tumors had a labyrinthine pattern, 22% glands, and 6% a festoon pattern. Papillae with a central blood vessel (Schiller-Duval bodies) were seen in one-third of the tumors but were numerous in only 5% of them. Nonspecific appearing papillae were seen in 10% of the tumors. A solid growth of cells with pale cytoplasm was seen in one-third of the tumors but was conspicuous in only half of that subset. The solid appearance was typically reminiscent of that of dysgerminoma, but lacked the septa and lymphocytic infiltrate of that neoplasm. Nine tumors had a component of cells with scant cytoplasm resulting in a blastema-like appearance and 3 had cells with abundant clear cytoplasm. Cords and clusters of cells were common but did not dominate the microscopic appearance. The stroma typically had a nonspecific collagenous to edematous appearance. Stromal luteinization was seen in 12 tumors; in 5 this was likely due to the patient being pregnant. Two tumors had minor foci of cells that resembled hepatocytes. Hyaline bodies were seen in most of the tumors and were often conspicuous. The neoplastic cells typically had modest amounts of lightly staining cytoplasm and only mild nuclear pleomorphism. Cells lining cysts were often flattened sometimes resulting in a deceptively innocuous appearance. Many of the tumors (mostly consultation cases), caused diagnostic difficulty; tumors in the differential diagnosis included clear cell carcinoma, embryonal carcinoma, Sertoli-Leydig cell tumor, and juvenile granulosa cell tumor. The patient age and marked elevation of the serum alpha-fetoprotein level (if measured) is helpful in many of these considerations. The overtly malignant gross appearance of most YSTs contrasts with certain other tumors in the differential and the association of some YSTs with dermoid cyst and many clear cell carcinomas with endometriosis may be helpful. The vast majority of ovarian YSTs are dominated microscopically by merging of reticular and cystic patterns which, although focally mimicked by other neoplasms, are in general characteristic, and distinctive features of other neoplasms are absent. Immunohistochemistry, particularly for alpha-fetoprotein and glypican 3, and lack of staining for various markers of other neoplasms is helpful but overlap exists and these results must be considered in the context of the overall clinical, gross, and microscopic features. YSTs dominated by hepatoid and glandular features are rare and their categorization as YSTs should be done cautiously if thoroughly sampled tumors show no evidence of classic features of YST emphasized herein and first elaborated by the Danish investigator Gunnar Teilum whose seminal observations have stood the test of time.

N. Raju KV, Rao TS, Sundaram C. The core four - A panel of immunohistochemistry markers to diagnose and subtype testicular germ cell tumors

Context:

Immunohistochemistry (IHC) to differentiate germ cell tumors.

Aims:

The aim of the study is to differentiate seminomatous and nonseminomatous germ cell tumors (GCTs) with morphological overlap using a minimal and affordable panel of IHC markers.

Settings and Design:

This is a retrospective observational study.

Subjects and Methods:

All testicular GCTs (TGCT) which were diagnosed on biopsies and/or resection specimens (prechemotherapy) between January 2014 and June 2019. The demographic, clinical, and imaging findings were noted from the medical records. Hematoxylin and eosin (H and E)-stained sections were reviewed for morphology. The IHC markers constituted Octamer-binding transcription factor (OCT) 3/4, glypican 3 (GPC3), CD117, CD30, placental-like alkaline phosphatase, Sal-like protein 4, and β-human chorionic gonadotropin (HCG). IHC markers were performed in various combinations depending on the morphology, and a panel constituting OCT 3/4, CD117, GPC3, and CD30 was performed on cases with diagnostic dilemma and morphological overlaps.

Statistical Analysis Used:

Sensitivity, specificity, positive (PPV), and negative predictive value (NPV) were calculated for suggested panel of IHC OCT 3/4, CD117, GPC3, and CD30.

Results:

The study included 36 patients with TGCT with a mean age of 27 (15–58) years. Nonseminomatous tumors were the most common (86%). The concise panel was performed in 20/36 (56%) tumors to resolve the diagnosis. The sensitivity, specificity, PPV, and NPV for OCT3/4 were 80%, 55%, 31%, and 92% in seminomas and 65%, 100%, 100%, and 46% in embryonal carcinomas (EC), for CD117 was 89%, 82%, 73%, and 93% in seminomas and 60%, 77%, 60%, and 77% in yolk sac tumors (YST), for GPC3 was 95%, 90%, 95%, and 90% in YST, CD30 96%, 100%, 100%, and 91% in ECs, respectively.

Conclusions:

Designing a novel concise and affordable IHC panel constituting OCT 3/4, CD117, GPC3, and CD30 has good sensitivity and specificity in differentiating seminomas, YST, and EC, respectively. Additional markers, namely β-HCG, can be used in identifying the choriocarcinoma component.

Primary mediastinal germ cell tumours: an immunohistochemical and molecular diagnostic approach

AIMS

Primary mediastinal germ cell tumours (PMGCTs) are rare mediastinal neoplasms and their diagnosis can be challenging due to small biopsy samples. The aim of this study was to elaborate a diagnostic algorithm using immunohistochemical stainings with focus on novel markers and molecular analysis of isochromosome 12p [i(12p)].

METHODS AND RESULTS

Paraffin-embedded tissues of 32 mediastinal tumours were analysed using immunohistochemical stainings for SALL4, LIN28, OCT3/4, D2-40, CD117, SOX17, SOX2, CD30, ß-hCG, GATA3, FOXA2, GPC3, AFP, TdT, NUT and pan-cytokeratin. Quantitative real-time polymerase chain reaction (qPCR) was performed to investigate i(12p) status. Fifteen seminomas, seven teratomas, one yolk sac tumour, one choriocarcinoma and seven mixed PMGCT were diagnosed. Each entity had different immunohistochemical staining patterns which helped to distinguish them: seminoma (OCT3/4, D2-40, CD117, TdT), embryonal carcinoma (OCT3/4, SOX2), yolk sac tumour (FOXA2, GPC3, AFP) and choriocarcinoma (ß-hCG, GATA3). Mature teratomas stained positive for pan-cytokeratin in epithelial components and focally for SALL4, SOX2, GATA3, D2-40 and FOXA2. Furthermore, a NUT carcinoma mimicking a PMGCT was diagnosed showing a strong nuclear SOX2 and speckled nuclear NUT staining. i(12p) was detected in 24 out of 27 PMGCTs [89%].

CONCLUSION

A diagnostic algorithm is of great importance for a reliable diagnosis of PMGCTs in the usually small tissue biopsy samples. Therefore, a combination of three to four antibodies to identify the correct histological subtype is usually necessary in addition to morphological features. The i(12p) status serves as an additional option to underline germ cell origin in selected cases.

Mediastinal Germ Cell Tumors: A Review and Update on Pathologic, Clinical, and Molecular Features

Mediastinal germ cell tumors (MGCTs) are the most common extragonadal germ cell tumors (GCTs) and most often arise in the anterior mediastinum with a male predilection. MGCTs also have a predilection for patients with Klinefelter syndrome and possibly other genetic conditions. MGCTs, as GCTs at other extragonadal sites, are thought to arise from germ cells improperly retained during migration along the midline during embryogenesis. Similar to their counterparts in the testes, MGCTs are classified into seminomatous and nonseminomatous GCTs. Seminomatous MGCT represents pure seminoma, whereas nonseminomatous MGCTs encompass pure yolk sac tumors, embryonal carcinoma, choriocarcinoma, mature or immature teratoma, and mixed GCTs with any combination of GCT types, including seminoma. Somatic-type or hematologic malignancies can also occur in association with a primary MGCT. MGCTs share molecular findings with GCTs at other sites, most commonly the presence of chromosome 12p gains and isochromosome i(12p). Treatment includes neoadjuvant chemotherapy followed by surgical resection of residual tumor, with the exception of benign teratomas, which require only surgical resection without chemotherapy. In this review, we highlight and provide an update on pathologic, clinical, and molecular features of MGCTs. Immunohistochemical profiles of each tumor type, as well as differential diagnostic considerations, are discussed.

Malignant Mixed Germ Cell Tumors of the Ovary: An Analysis of 100 Cases Emphasizing the Frequency and Interrelationships of Their Tumor Types

One hundred malignant mixed germ cell tumors of the ovary that occurred in patients 3 to 55 years (mean: 20 y) of age are described. The clinical presentation was usually that of any highly malignant tumor of the ovary (abdominal pain and distension), but rarely (3 cases) endocrine manifestations were present. The tumors were usually unilateral (96%), ranged from 4 to 38 cm (mean: 16 cm), and were uniformly solid or, more often, solid and cystic; occasionally the typical appearance of dysgerminoma could be appreciated. The most common tumor type was yolk sac tumor (91%), followed by dysgerminoma (61%), immature teratoma (58%), embryonal carcinoma (38%), and choriocarcinoma (11%). A variety of admixtures were encountered; dysgerminoma and yolk sac tumor was the most common combination (25% of the tumors) with the 2 components often being sharply demarcated. Immature teratoma and yolk sac tumor was the next most common pairing (20%) followed by yolk sac tumor and embryonal carcinoma, with or without immature teratoma (16%). Tumors with a choriocarcinoma component had the most varied combinations of tumor types. Embryoid bodies were seen in 21% of the tumors, most often as fragmented forms arranged in a nodular manner with yolk sac tumor and/or embryonal carcinoma; uncommonly they occurred singly or in clusters. Numerous confluent well-formed embryoid bodies (polyembryoma) were prominent in 2 tumors. Three tumors had a focal diffuse embryoma pattern. The specific tumor types showed the known diverse spectrum of microscopic appearances, but the frequent haphazard arrangement of 2 or more subtypes often resulted in complex morphology. Overgrowth of another neoplastic component, most often primitive neuroectodermal tumor, occurred in 10% of the tumors further complicating the histologic picture. This is the largest series of ovarian malignant mixed germ cell tumors reported and details their characteristics including associations of their subtypes and the frequent apparent role of embryoid bodies in giving rise to yolk sac tumor and embryonal carcinoma components.

Dysgerminoma of the Ovary: An Analysis of 140 Cases Emphasizing Unusual Microscopic Findings and Resultant Diagnostic Problems

One-hundred fourty pure dysgerminomas were evaluated with particular focus on the microscopic features as seen in 125 cases with available slides. The patients ranged from 8 to 59 years of age (mean, 24.1 y). The tumors, bilateral in 4% of the cases and with a mean tumor diameter of 13 cm, were typically soft, lobulated, homogeneous, and creamy white to tan to yellow but necrosis was found in 13%, hemorrhage in 20%, and focal cystic change in 15%. On microscopic examination, the patterns and other notable features encountered, including their frequency, were as follows: an alveolar pattern resulting from delicate fibrovascular septa (51%), diffuse (33%), macronodular (14%), insular (26%), cords (28%), solid tubular (17%), microspaces (sometimes simulating glands) (12%), follicle-like spaces (5%), prominent fibrous bands (65%), stromal edema (56%), stromal luteinization (9%), granulomatous infiltrate (46%), lymphocytic infiltrate (100%), Langhans cell type giant cells (35%), syncytiotrophoblast giant cells (6%), prominent population of cells with pale to clear cytoplasm (73%), cells with amphophilic to eosinophilic cytoplasm (53%) and vacuolated occasionally signet ring-like cells (7%). Various constellations of the above findings often resulted in an appearance different from that usually portrayed in the literature and certain tumors of very different nature being in the differential such as undifferentiated carcinoma not otherwise specified, small cell carcinoma of hypercalcemic type, and malignant lymphoma. The correct diagnosis can be arrived at by considering the usual relative youth of the patient, often rather characteristic gross features, and most crucially careful attention to the microscopic features and awareness of variant morphologic findings. Those that are particularly problematic based on this study are diffuse growth with inconspicuous fibrovascular septa, macronodules, cords, solid tubular formations, spaces ranging from small to large, and mimicking glands or follicles, prominent fibrous to edematous stroma, and cells with amphophilic to eosinophilic cytoplasm. According to the degree of difficulty and confidence of the interpreter, well-known immunohistochemical features of dysgerminoma, which largely differ from those of other neoplasms in the differential, will aid if felt indicated.

Pure primary yolk sac tumor of the endometrium tends to occur at a younger age: A case report and literature analysis

We present a case of primary yolk sac tumor of the endometrium. This rare tumor occurred in a 43-year-old woman with a pure primary yolk sac tumor. The tumor resembled yolk sac tumor morphology of the ovary. Tumor cells expressed SALL4, AFP, GPC-3, and AE1/AE3 and were focal positive for PAX8. EMA, ER, and PR, among others, were negative. We further analyzed 29 reported cases of this rare tumor in the literature. In total, 17 of 30 patients (57%) had pure endometrial yolk sac tumor, and 13 (43%) had a concomitant somatic neoplasm (endometrial adenocarcinoma was the most common). Although the average age was 52 years (range: 24–87 years), patients with pure yolk sac tumor were younger than those with concomitant somatic tumors, with a mean age of 44.41 years (24–68 years) versus 61.92 years (28–87 years), P = 0.008. Patients with endometrial yolk sac tumor combined with somatic tumor tend to have a slightly higher stage and a poor prognosis.

Vaginal Yolk Sac Tumor: A Case Series and Review of the Literature

OBJECTIVE

To report diagnosis, treatment, and outcomes of vaginal yolk sac tumor (YST) cases at a single institution and review literature on vaginal YST to outline advancements in diagnosis, treatment, and survival.

DESIGN

Retrospective chart review of female patients less than 21 years of age with pathologic diagnosis of vaginal YST treated at a large children's hospital, and summary of a 100-year review of the literature on vaginal yolk sac tumor.

SETTING

Children's Healthcare of Atlanta, a tertiary center in Atlanta, GA.

PARTICIPANTS

Female patients less than 21 years of age diagnosed with vaginal YST.

RESULTS

Two cases of vaginal YST at our institution are outlined. Both patients presented within the first 2 years of life with vaginal bleeding and were treated successfully with chemotherapy alone. After review of the literature, 137 cases of vaginal YST were found. The mean age at diagnosis was 11 months, and all patients presented with vaginal bleeding. Before 2000, more radical treatments were pursued, and 40% resulted in death. Since the year 2000, treatment has shifted toward chemotherapy and more conservative surgical management, with 51% of vaginal YST cases treated with chemotherapy alone with 92% of patients alive at time of publication.

CONCLUSION

Our cases contribute to the limited literature demonstrating the efficacy of conservative management of rare cases of vaginal YST with chemotherapy alone. This case series and review of the literature provide mounting evidence that vaginal YST should be in the differential diagnosis in young girls with vaginal tumors, and conservative management of vaginal YST has excellent outcomes.

HNF1β is a sensitive and specific novel marker for yolk sac tumor: a tissue microarray analysis of 601 testicular germ cell tumors

Hepatocyte Nuclear Factor 1 beta (HNF1β) is a transcription factor which plays an important role during early organogenesis, especially of the pancreato-biliary and urogenital tract. Furthermore, HNF1β is an established marker in the differential diagnosis of ovarian cancer and shows a distinct nuclear expression in the clear cell carcinoma subtype. Recently, it has been described in yolk sac tumor, which represents a common component in many non-seminomatous germ cell tumors. Due to its broad histologic diversity, the diagnosis may be challenging and additional tools are very helpful in the workup of germ cell tumors. Immunohistochemistry was used to study HNF1β expression in a tissue microarray (TMA) of 601 testicular germ cell tumors including seminoma, embryonal carcinoma, yolk sac tumor, choriocarcinoma, teratoma, germ cell neoplasia in situ (GCNIS), and normal tissue. The expression pattern was compared to glypican 3 (GPC3) and α-fetoprotein (AFP), two markers currently in use for the detection of yolk sac tumor. HNF1β showed a distinct nuclear staining in comparison to the cytoplasmic pattern of GPC3 and AFP. The sensitivity and specificity of HNF1β were 85.4% and 96.5%, of GPC3 83.3% and 90.7%, of AFP 62.5% and 97.7%. We conclude that HNF1β allows a reliable distinction of yolk sac tumor from other germ cell tumor components. Therefore, we propose HNF1β as a novel and robust marker in the immunohistochemical workup of testicular germ cell tumors.

Metastatic Mixed Germ Cell Tumour with Embryonal Carcinoma and Choriocarcinoma in a Female Eurasian Harvest Mouse (Micromys minutus)

Mixed germ cell tumours occur rarely in veterinary species. This report describes a case of metastatic mixed germ cell tumour in a female Eurasian harvest mouse (Micromys minutus). The tumour was extensive in one ovary and the uterus, and was characterized by two distinct tumour cell populations with features typical of embryonal carcinoma (EC) and choriocarcinoma (CC). Metastases of CC to the lungs and liver were observed. The exact origin of the CC was unclear, but the possibility of a non-gestational CC is favoured, given the context of a mixed germ cell tumour and lack of p53 expression. EC diagnosis was confirmed by immunohistochemical labelling of CD30 and lack of immunoreactivity for c-Kit. In addition, membranous β-catenin expression was present in the EC component, indicating an inactive Wnt/β-catenin pathway, which is required for the maintenance of pluripotency.

SALL4 is a useful marker for pediatric yolk sac tumors

BACKGROUND

SALL4 is a zinc finger transcription factor that exerts its physiological role during embryo-fetal development. Analyses of SALL4 expression have shown its oncogenic role in precursor B-cell lymphoblastic lymphoma, acute and chronic myeloid leukemia, gastrointestinal, breast, and lung cancers. The aim of this study was to determine the immunohistochemical profile of SALL4 in pediatric yolk sac tumors (YSTs).

METHODS AND RESULTS

Immunohistochemistry detection of SALL4 was performed in 22 cases of pediatric YSTs and 10 mature teratomas. The percentage of tumor cells stained was scored as 0, 1+ (1-30% cells), 2+ (31-60%), 3+ (61-90%), and 4+ (> 90%). To compare its sensitivity and specificity with Glypican-3 and α-fetoprotein (AFP), we also stained tumors from these cases for Glypican-3 and AFP. In contrast to AFP and glypican-3, SALL4 staining in more than 90% of the tumor cells was seen in all 22 pediatric YSTs (100% sensitivity) (P < 0.001 for both SALL4 vs. AFP and SALL4 vs. glypican-3).

CONCLUSIONS

SALL4 is a sensitive marker for pediatric YSTs and it can be used to distinguish them from mature teratomas. SALL4 is likely to become a new and valuable biomarker for the diagnosis of pediatric YST.

Ovarian tumors: a survey of selected advances of note during the life of this journal

The author reviews highlights of advances in knowledge concerning ovarian tumor pathology since the time of an essay in the first issue of this Journal written by Dr Robert E. Scully, who, both before and for several decades after the Journal was instituted, made many original contributions to the field and was the major architect of the 1973 World Health Organization classification of ovarian tumors which was much more clear and logical than prior ones. The current review considers the neoplasms in essentially the same order as was done in the first issue of this journal and presents a personal look at the highlights of new information concerning various well-known categories, surface epithelial, germ cell, sex cord-stromal, metastatic neoplasms and briefly, benign so-called tumor-like lesions. Some of the most notable developments are as follows: (1) an orderly approach to the classification of implants of serous borderline tumors into noninvasive and invasive categories; (2) recognition of distinctive micropapillary patterns seen in some borderline tumors and low-grade carcinomas; (3) a remarkable propensity for some endometrioid carcinomas to mimic sex cord- stromal tumors; (4) appreciation of the differences between primary mucinous tumors of intestinal and müllerian types; (5) the importance of distinguishing within primary mucinous carcinomas between expansile and destructive stromal invasion; (6) emphasis on the diagnosis of immature teratoma being based on the presence of primitive-embryonic-appearing tissues; (7) appreciation of variant morphology of cases of struma ovarii which may lead to significant diagnostic problems; (8) subdivision of granulosa cell tumors into adult and juvenile types because of the differing features of the two groups including in the second category the propensity for more malignant neoplasms to be mimicked; (9) recognition of a distinctive form of Sertoli-Leydig cell tumor, the retiform variant, with a propensity to occur in the young; (10) appreciation of a unique highly malignant neoplasm that typically afflicts the young and may be associated with hypercalcemia, so-called small cell carcinoma of hypercalcemic type; (11) greater awareness than was hitherto the case of the propensity for metastatic intestinal adenocarcinoma to mimic primary endometrioid carcinoma and similarly for metastatic mucinous carcinomas to simulate primary mucinous cystic tumors; (12) recognition of the distinctive features of low-grade appendiceal mucinous neoplasms that spread to the ovary and are typically associated with pseudomyxoma peritonei; and (13) appreciation that the histologic spectrum seen in cases of Krukenberg tumor is broader than often previously thought.

Pitfalls in the interpretation of specimens from patients with testicular tumours, with an emphasis on variant morphologies

Accurate diagnosis of primary and metastatic tumours is essential in testicular cancer. While many cases are straightforward, some pose difficulties, especially when variant morphologies occur. Seminoma with 'atypical' features, including increased nuclear pleomorphism and crowding and greater cytoplasmic density with loss of membrane definition, mimics embryonal carcinoma, although ancillary features (fibrous septa, lymphocytes) and immunohistochemistry are of great help. Other deceptive seminoma features include prominent to exclusive intertubular growth, microcystic/tubular patterns, and signet-ring tumour cells. Conversely, embryonal carcinomas may have 'seminoma-like' foci, as may Sertoli cell tumours with diffuse growth and pale cytoplasm. Solid pattern yolk sac tumour mimics seminoma and, conversely, microcytic seminoma resembles yolk sac tumour. Other architectural patterns, ancillary yolk sac tumour features (intercellular basement membrane deposits, hyaline cytoplasmic globules) and immunohistochemistry aid in distinction from seminoma. Embryonal carcinomas may show, in addition to 'seminoma-like' foci, pseudoendodermal sinus-like structures, sieve-like patterns, endometrioid-like morphology and prominent zones of stratified columnar tumour cells. These may cause confusion with yolk sac tumour and teratoma, although careful attention to cytological features usually suffices for accurate diagnosis. Recent work has defined 'new' primary trophoblastic tumours, i.e., cystic trophoblastic tumour and epithelioid trophoblastic tumour. The newly termed 'spermatocytic tumour' occasionally consists mostly of a monotonous proliferation of intermediate-sized tumour cells with prominent nucleoli, thereby simulating either seminoma or embryonal carcinoma. Prostatic adenocarcinoma remains the most common tumour to metastasise to the testis and can cause confusion with rete carcinomas and primary germ cell tumours. Post-chemotherapy resections pose their own challenges. Effete tumour cells in areas of necrosis and prominent fibroxanthomatous reactions should not be interpreted as persistent, viable germ cell tumour. 'Fibrosis' often has atypical widely scattered spindle tumour cells in a densely collagenous background but does not merit additional treatment apart from excision. The marked cytological atypia that may occur in metastatic teratoma may be disconcerting but, again, the proper treatment is complete surgical excision rather than more chemotherapy. Glandular and sarcomatoid yolk sac tumours, which are almost exclusively seen after chemotherapy, resemble adenocarcinomas and sarcomas, respectively. Unlike de novo malignancies, they are mostly seen in sites expected for metastases.

ZBTB16 is a sensitive and specific marker in detection of metastatic and extragonadal yolk sac tumour

AIMS

Accurate histological diagnosis and classification of germ cell tumours (GCTs) is key to informing successful therapeutic and surveillance strategy. The modern therapeutic approach for yolk sac tumour (YST) is highly curative. Because YST takes on a large morphological spectrum, it can be confused for other GCT subtypes as well as somatic carcinomas, particularly when YST presents in an extragonadal or a metastatic setting. Currently available immunohistochemical markers are limited by suboptimal sensitivity and specificity. We reported recently that ZBTB16 is a sensitive and specific marker for testicular YST. ZBTB16 is absent in other GCTs and in most common somatic carcinomas, including those of gastrointestinal, pancreatobillary, respiratory, genitourinary and gynaecological tracts. The purpose of this study is to investigate the diagnostic utility of ZBTB16 in the settings of metastatic and extragonadal YST.

METHODS AND RESULTS

We studied 32 archived metastatic and four extragonadal primary YSTs as well as 51 somatic malignancies for their immunohistochemical expression of ZBTB16. For comparison, α-fetoprotein (AFP) and glypican-3 were also studied in parallel. Our results demonstrated an overall sensitivity of 91.6% for ZBTB16 in detecting metastatic and extragonadal YSTs. The non-YST elements (teratoma and embryonal carcinoma) in 15 YST-containing metastatic mixed GCTs were non-reactive. With the exception of occasional myoepithelial cells of salivary gland carcinoma, all the 51 somatic malignancies were negative for ZBTB16.

CONCLUSIONS

ZBTB16 is a sensitive and specific marker for YST and is diagnostically superior to AFP and glypican-3 in metastatic and extragonadal settings.

High-level expression of divergent endodermal lineage markers in gonadal and extra-gonadal yolk sac tumors

Yolk sac tumors occur at both gonadal and extra-gonadal sites. A recent case of ovarian endometrioid-pattern yolk sac tumor with strong diffuse expression of TTF-1 illustrated the potential for misdiagnosis due to divergent expression of endodermal lineage markers. The aim of this study was to investigate the expression of four divergent endodermal lineage markers, TTF-1, CDX2, Hep Par 1, and Napsin A, in gonadal and extra-gonadal yolk sac tumors of differing age, sex, and location (excluding foci of overt hepatoid differentiation). We identified 26 cases (5 ovarian, 15 testicular, and 6 extra-gonadal) containing yolk sac tumor as identified by typical histology and confirmed by positive immunohistochemical staining for alpha-fetoprotein and glypican-3. Mixed or ambiguous foci were confirmed by immunohistochemistry (SALL4 positive and Oct-4 negative). The relative proportion of three histologic patterns: reticular/cystic, solid/myxoid, and glandular was estimated. Percent positivity for the four divergent endodermal lineage markers was compared within yolk sac tumor areas according to site, age group, and histologic pattern. High-level (>25%) staining for one or more divergent endodermal lineage markers was seen in eleven cases: Hep Par 1 in seven cases, all post-pubertal, TTF-1 in four cases, two ovarian and two extra-gonadal, and CDX2 in three cases, with no age or site predilection. No case highly expressed all three divergent endodermal lineage markers, but four co-expressed high levels of two markers: two ovarian yolk sac tumors with TTF-1 and Hep Par 1, one testicular yolk sac tumor with CDX2 and Hep Par 1, and one extra-gonadal yolk sac tumors with TTF-1 and CDX2. While no absolute correlation of high-level divergent endodermal lineage marker expression with histologic subtype was observed, TTF-1 and CDX2 expression was predominantly seen in reticular/cystic and glandular areas while Hep Par 1 was most frequent in myxoid/solid and glandular areas.

Tumors of the Testis: Morphologic Features and Molecular Alterations

This article reviews the most frequently encountered tumor of the testis; pure and mixed malignant testicular germ cell tumors (TGCT), with emphasis on adult (postpubertal) TGCTs and their differential diagnoses. We additionally review TGCT in the postchemotherapy setting, and findings to be integrated into the surgical pathology report, including staging of testicular tumors and other problematic issues. The clinical features, gross pathologic findings, key histologic features, common differential diagnoses, the use of immunohistochemistry, and molecular alterations in TGCTs are discussed.

ZBTB16: a novel sensitive and specific biomarker for yolk sac tumor

Although the function of zinc finger and BTB domain containing 16 (ZBTB16) in spermatogenesis is well documented, expression of ZBTB16 in germ cell tumors has not yet been studied. The aim of this study was to investigate the immunohistochemical expression and diagnostic utility of ZBTB16 in germ cell tumors. A total of 67 adult germ cell tumors were studied (62 testicular germ cell tumors, 2 ovarian yolk sac tumors, 1 mediastinal yolk sac tumor, and 2 retroperitoneal metastatic yolk sac tumors). The 62 testicular primary germ cell tumors are as follows: 34 pure germ cell tumors (20 seminomas, 8 embryonal carcinomas, 2 teratomas, 1 choriocarcinoma, 1 carcinoid, and 2 spermatocytic tumors) and 28 mixed germ cell tumors (composed of 13 embryonal carcinomas, 15 yolk sac tumors, 15 teratomas, 7 seminomas, and 3 choriocarcinomas in various combinations). Thirty-five cases contained germ cell neoplasia in situ. Yolk sac tumor was consistently reactive for ZBTB16. Among the 15 testicular yolk sac tumors in mixed germ cell tumors, all displayed moderate to diffuse ZBTB16 staining. ZBTB16 reactivity was present regardless of the histologic patterns of yolk sac tumor and ZBTB16 was able to pick up small foci of yolk sac tumor intermixed/embedded in other germ cell tumor subtype elements. Diffuse ZBTB16 immunoreactivity was also observed in 2/2 metastatic yolk sac tumors, 1/1 mediastinal yolk sac tumor, 2/2 ovarian yolk sac tumors, 2/2 spermatocytic tumors, 1/1 carcinoid, and the spermatogonial cells. All the other non-yolk sac germ cell tumors were nonreactive, including seminoma (n=27), embryonal carcinoma (n=21), teratoma (n=17), choriocarcinoma (n=4), and germ cell neoplasia in situ (n=35). The sensitivity and specificity of ZBTB16 in detecting yolk sac tumor among the germ cell tumors was 100% (20/20) and 96% (66/69), respectively. In conclusion, ZBTB16 is a highly sensitive and specific marker for yolk sac tumor.

Radiological-pathological correlation of yolk sac tumor in 20 patients

BACKGROUND

Yolk sac tumor (YST) is a rare tumor. Familiarity of its radiological characteristics may permit preoperative diagnosis and improve surgical management of patients. However, a detailed description of the imaging features of YST with pathological correlation in particular is scarce.

PURPOSE

To investigate computed tomography (CT) findings of YSTs with pathological correlation.

MATERIAL AND METHODS

CT images of 20 patients with pathologically proven YST were retrospectively reviewed. The location, size, margin, internal architecture, and pattern and degree enhancement of the lesion were evaluated. Radiological findings were correlated with pathological results.

RESULTS

The locations of 20 tumors were distributed between the testis (n = 3), ovary (n = 6), sacrococcygeal area (n = 6), rectum (n = 1), and mediastinum (n = 4). The median age was 13 years. On CT images, all tumors were seen as oval (n = 14) or irregular (n = 6), well-defined (n = 16) or ill-defined (n = 4) masses with a mean size of 9.7 cm. The lesions were solid cystic (n = 10), entirely solid (n = 6), or predominantly cystic (n = 4). Intratumoral hemorrhage, calcification, and fatty tissue were seen in nine, three, and two tumors, respectively. Discontinuity of the tumor wall was seen in eight tumors. After contrast media administration, most tumors showed heterogeneous moderate to marked enhancement (n = 7) or heterogeneous marked enhancement (n = 9). Enlarged intratumoral vessels were seen in 17 tumors.

CONCLUSION

YST usually appears as a large solid-cystic mass with intratumoral hemorrhage, capsular tear, marked heterogeneous enhancement, and enlarged intratumoral vessels on CT images. Intratumoral calcification and fatty tissue, although rare, may indicate a mixed YST containing teratoma component.

The Utility of Immunohistochemistry in the Differential Diagnosis of Gynecologic Disorders

Context

Immunohistochemistry has assumed an increasing role in the identification and characterization of gynecologic disorders including lesions with deceptively bland morphology, uncommon and underdiagnosed neoplasms, and neoplasms with specific genetic alterations associated with overexpression or loss of expression of specific proteins. The diagnostic accuracy has been significantly improved owing to the discovery and increasing experience with the tumor-associated biomarkers, and the increasing demand for precise tumor classification to assess suitability for the expanding therapeutic modalities including clinical trials.

Objective

To differentiate lesions of the gynecologic tract through the use of effective immunohistochemical panels.

Data Sources

Literature review and authors' personal practice experience.

Conclusions

The application of diagnostic and prognostic immunohistochemical panels has enabled pathologists to better guide therapeutic decisions and to better predict the clinical outcome. It is now well established that the use of ancillary testing, including immunohistochemistry, has a significant power in the identification, differentiation, and classification of reactive, premalignant, and malignant gynecologic disorders. This article discusses the utilities and pitfalls of the commonly used immunohistochemical markers in the context of overlapping morphologic features encountered in the uterus, ovaries, and fallopian tubes.

Testicular yolk sac tumors in children: a review of 61 patients over 19 years

BACKGROUND

To describe 19 years of clinical experience managing pediatric patients with testicular yolk sac tumors at the Chongqing Medical University Affiliated Children's Hospital.

METHODS

This study involved a retrospective review of the records of 61 pediatric patients who presented with testicular yolk sac tumor at our institution between 1995 and 2014.

RESULTS

All patients presented with a painless scrotal mass. Serum alpha-fetoprotein (AFP) levels were elevated (n = 15). Ultrasonography identified the yolk sac tumors as solid masses. Color Doppler flow imaging showed rich blood flow inside and around the masses in 84.8% cases. X-ray of the scrotum showed no intrascrotal calcification (n = 38). Inguinal orchiectomy was performed in 60 patients, one case was treated with testis-sparing surgery. In 11 cases, radical dissection of the inguinal lymph nodes was performed. Histological analysis showed pathologies typical of yolk sac tumor including microcapsule and reticular structures, gland tube-gland bubble structures, an embryo sinus structure, and papillary structures. All patients received postoperative chemotherapy. Serum AFP levels returned to normal 1 to 2 months after surgery. No patients treated with surgery in our hospital relapsed.

CONCLUSION

Testicular yolk sac tumor presents as a painless scrotal mass, increased serum AFP levels, and a solid mass on ultrasound. Chest radiography and abdominal ultrasound should be used to accurately stage the tumor. We advocate for inguinal orchiectomy for Stage I disease and postoperative chemotherapy to prevent recurrence in the ipsilateral or contralateral testis.

The yolk sac tumor: reflections on a remarkable neoplasm and two of the many intrigued by it-Gunnar Teilum and Aleksander Talerman-and the bond it formed between them

One of the most remarkable of human neoplasms, the yolk sac tumor, is reviewed, emphasizing its histologic diversity and differential diagnosis, occurrence at many sites, and the shared passion for this unique neoplasm of Dr Gunnar Teilum (who deserves almost all credit for delineation of the nature of the tumor and its features) and Dr Aleksander Talerman (who made his own contribution to our knowledge of it) and the friendship it helped forge between these 2 distinguished pathologists. In a unique series of articles, beginning in the early 1940s, Teilum delineated the distinctive features of the neoplasm and recognized that it was 1 of 2 initially included as "mesonephroma ovarii" by Dr Walter Schiller in 1939 (the second we now know as clear cell carcinoma). Teilum named the tumor "endodermal sinus tumor" because it came to his attention that papillary formations common in the yolk sac tumor resembled the endodermal sinuses of the rat placenta. He focused on the histogenesis of the tumor and its morphologic features culminating in a classic paper in Cancer in 1959. Although Teilum and others recognized that yolk sac tumor could be a component of mixed germ cell tumors, Talerman was one of the first to emphasize that, particularly in the testis, it was common to see yolk sac tumor as a component of a mixed germ cell tumor. Teilum, working in Copenhagen, and Talerman, when the former was alive, working in Rotterdam, developed a warm friendship in part due to their great interest in the yolk sac tumor, although it also extended to other areas of gonadal neoplasia and indeed beyond the boundaries of medicine when they shared time together. The typical histologic features of the yolk sac tumor are the reticular-microcystic patterns Teilum described, but various other patterns, including solid and even rarer ones such as glandular and hepatoid, are now well known. There are some interesting variations in the age distribution of this tumor at various sites: for example, vaginal examples are almost restricted to children under 2 years of age; those of the testis that are pure also occur mostly in young boys (average age about 20 months) but are occasionally seen in later years; ovarian examples peak at about 19 years of age; mediastinal forms are mostly restricted to young adult males. Brief consideration is also given to the occurrence of this tumor at well-known extragonadal sites such as retroperitoneum, mediastinum, and pineal as well as more exotic locations. Note is made of the recently emphasized occurrence of the yolk sac tumor on the background of a somatic neoplasm, most often endometrioid carcinoma of the ovary. Given the wide ranging and fascinating clinical and pathologic aspects of the neoplasm, it is no surprise that it continues to be a source of great interest to any pathologist who sees one or more examples, and we are indebted to Dr Teilum for his monumental studies and to Dr Talerman for his own contributions.

Discovery and diagnostic value of a novel oncofetal protein: glypican 3

Glypican 3 is a membrane-bound heparan sulfate proteoglycan, which has recently been identified as a marker for liver cancer and germ cell malignancies. Individuals with loss-of-function mutations for the glypican 3 gene exhibit Simpson-Golabi-Behmel syndrome, a rare X-linked overgrowth disorder. Expression of glypican 3 mRNA and protein is normally silenced in most adult organs and may reappear during malignant transformation. In the past few years, immunohistochemical and molecular characteristics of glypican 3 in hepatocellular carcinoma have been elucidated. More recently, glypican 3 has been emerging as a new diagnostic marker for germ cell tumors and especially testicular and ovarian yolk sac tumors. However, in other tumors such as renal cell carcinomas, squamous cell carcinomas, and melanomas, studies disagree on the level of glypican 3 expression. Finally, there is the controversial notion of glypican 3 as a tumor suppressor gene. In this review article, we update current knowledge on glypican 3 expression in normal and neoplastic tissues, evaluate its utility as a tumor marker in clinical practice, and explore its role as a novel oncofetal protein with clinical implications. Our focus is on the diagnostic value of glypican 3 in germ cell tumors and other neoplasms in addition to hepatocellular carcinoma. In conclusion, glypican 3 has been proven to be a useful immunohistochemical marker in distinguishing yolk sac tumors, choriocarcinomas, and Wilms tumors from other malignancies histologically mimicking these primitive tumors. Clinically, we recommend that glypican 3 be used as part of a panel of markers in subtyping testicular germ cell tumors.

Germ cell tumors of the ovary: an update

CONTEXT

The field of ovarian germ cell tumors (OGCTs) has remained relatively unchanged in the last 2 decades. However, the introduction of new stem cell pluripotency markers has provided a new understanding into the identification and taxonomy of OGCT types. New data have provided new insights into unusual teratoma-associated autoimmune disorders and the origin of gliomatosis peritonei.

OBJECTIVE

To review the impact of new pluripotency markers in the diagnosis of malignant OGCT (MOGCT) and analyze new nomenclature proposals and clinicopathologic entities.

DATA SOURCES

Ovarian germ cell tumors from routine material and expert consultation files at San Cecilio University Hospital, Granada, Spain, and the relevant literature were reviewed.

CONCLUSIONS

Although a correct diagnosis of MOGCT can often be made with histologic and classic immunohistochemical studies, the new immunohistochemical pluripotency markers give higher diagnostic accuracy. Germ cell tumors represent a caricature of the phases of normal embryonic differentiation from primordial germ and stem cells to extraembryonal and somatic tissue differentiation. Since every stage of differentiation and its related tumor type exhibit characteristic markers, the analysis of their expression facilitates tumor typing, thus complementing the use of classic antibodies. They also allow a more precise evaluation of the degree of immaturity in teratoma. The new term, primitive endodermal tumors, simplifies the understanding of the complex histology of the yolk sac tumor group, as this terminology encompasses its multiple endodermal differentiations. Recently described autoimmune encephalitis due to antibodies against the N-methyl-d-aspartate receptor has become the most frequent autoimmune disorder associated with ovarian teratoma.

[Testicular seminomas. The classical and the less classical ones]

Testicular germ cell tumors are generally rare but represent the most common solid neoplasms in young men. They are subdivided into seminomas and non-seminomatous germ cell tumors. Usually the diagnosis of a seminoma is straightforward due to the characteristic morphology, although problems in differential diagnosis can occur because of unusual histological growth patterns. This article describes the challenging differential diagnosis with respect to seminomas versus non-seminomatous germ cell tumors, sex cord stromal tumors, lymphomas and non-neoplastic conditions, such as scars and inflammatory changes. In addition, prognostic factors for seminomas are presented and discussed.

Gastric adenocarcinoma with yolk sac tumor differentiation and liver metastasis of yolk sac tumor component

Gastric adenocarcinoma with yolk sac tumor (YST) differentiation has rarely been reported. We report a case of primary gastric adenocarcinoma with yolk sac tumor differentiation and liver metastases of the YST component in a 50-years-old patient. This was suspected due to high serum level of alpha fetoprotein in the presence of a gastric fundal tumor. Gastric carcinoma with yolk sac tumor component is a rare entity with a poor prognostic outcome.

CDX-2 expression in malignant germ cell tumors of the testes, intratubular germ cell neoplasia, and normal seminiferous tubules

CDX-2 is a caudal-type homeobox gene, encoding a transcription factor that plays an important role in proliferation and differentiation of intestinal epithelial cells. The utility of antibodies to CDX2 in the identification of adenocarcinomas of the gastrointestinal tract, particularly colorectal adenocarcinomas, in both primary and metastatic settings is well established. It is well-known that patients with testicular tumors may occasionally lack an obvious palpable mass. However, the expression of CDX2 in malignant germ cell tumors of the testes which have metastatic potential has not been previously studied in a large series. A tissue microarray was constructed from 52 malignant germ cell tumors of the testes including: 29 cases of classic seminoma, 8 cases of embryonal carcinoma, 8 cases of yolk sac tumor, 4 cases of malignant teratoma, 2 cases of choriocarcinoma, and 1 case of spermatocytic seminoma. Ten cases of intratubular germ cell neoplasia and seven cases of benign testicles with normal seminiferous tubules were also included in tissue microarray. Immunohistochemical stains for CDX2 was performed and analyzed. Only nuclear staining was considered positive. Positive expression of CDX2 was identified in 2/2 cases (100 %) of choriocarcinoma, 4/8 cases (50 %) of teratoma, 3/8 cases (38 %) of embryonal carcinoma, 3/8 cases (38 %) of yolk sac tumor, and 1/29 cases (3 %) of classic seminoma. CDX2 was negative in all cases of intratubular germ cell neoplasia, normal seminiferous tubules, and the only case of spermatocytic seminoma. The role of CDX-2 in the differentiation of intestinal/enteric epithelial cells may contribute to the formation of trophoblastic, glandular, villous, or cystic structures in germ cell tumors of the testes. This study suggests that the expression of CDX2 in a variety of malignant germ cell tumors of the testes may be a potential pitfall in metastatic tumors of unknown primary, which are thought to be of gastrointestinal/colorectal origin but are actually from a clinically occult testicular tumor.